Enter your room details for an instant estimate.
Room Dimensions
Openings & Coats
~20 ft² each
~15 ft² each
Recommended: 2
Ceiling & Primer
Paint Details
Default: 350 ft²/gal
Used to calculate how many cans to buy
Recommended: 10–15%
Optional — for cost estimate
Your Estimate
Enter your room dimensions above to see your paint estimate.
This Paint Calculator helps you determine exactly how much paint and primer you need for any room project. No more guesswork or wasted materials.
Calculate paint requirements with precision. Enter your room dimensions and get instant results for:
Wall and ceiling coverage in square feet or meters
Exact gallons needed for paint and primer
Total project cost with customizable pricing
Multiple coat calculations for walls and ceilings
Flexible room shapes. Rectangle, L-shaped, or vaulted ceilings—all supported.
Smart deductions. Automatically subtracts door and window areas from your calculations.
Imperial or metric. Switch between feet and meters instantly.
Waste factor included. Accounts for spillage and overage (adjustable 0-20%).
Optional primer calculations. Toggle primer on/off with separate coverage rates.
Real-time validation. Catch errors before you calculate.
Home improvement projects. Professional painters. DIY enthusiasts. Interior designers estimating materials.
Get accurate paint estimates in seconds. Stop overbuying or running short mid-project.
A paint calculator is a digital tool that determines the amount of paint required to cover a specific surface area based on room dimensions, number of coats, and paint coverage rates.
You input wall measurements, ceiling height, and the number of doors or windows. The calculator processes these numbers and tells you exactly how many gallons of paint you need.
Most paint calculators account for standard coverage rates (around 350-400 square feet per gallon) and let you adjust for multiple coats or different paint types.
The tool starts with basic room dimensions - length, width, and ceiling height. It calculates total wall area by multiplying these measurements.
Next, it subtracts non-paintable surfaces. Doors typically count as 20 square feet each, windows vary but average around 15 square feet.
The calculator divides your total paintable area by the coverage rate per gallon. If you're applying two coats, it doubles the paint quantity. Some advanced versions factor in paint wastage (usually 10%) to prevent you from running short mid-project.
The final output shows gallons needed, often broken down by primer and topcoat if you've specified both.
Accurate measurements make the difference between buying too much paint or making emergency runs to the store.
Wall length and height are your starting points. Measure each wall individually if your room isn't a perfect rectangle - alcoves, bump-outs, and angled walls throw off quick estimates.
Ceiling dimensions matter for rooms where you're painting overhead surfaces. Cathedral ceilings or vaulted spaces need different calculations than standard 8-foot flat ceilings.
Don't forget trim and baseboards. These eat up more paint than you'd think, especially crown molding with intricate details in interior design that require careful coverage.
Multiply wall length by height for each wall. Add all four walls together for total wall area.
Slanted walls or walls with weird angles? Break them into rectangles and triangles, calculate each section separately, then sum them up.
Length times width gives you ceiling square footage. Easy for rectangles.
Angled or cathedral ceilings require you to measure the actual sloped surface, not just the floor plan footprint.
Standard interior doors are roughly 21 square feet (7 feet high by 3 feet wide). Exterior doors run slightly larger.
Windows vary wildly. Measure height and width, multiply, then round up to be safe. Bay windows and picture windows need individual attention.
One gallon of paint typically covers 350 to 400 square feet on smooth, primed surfaces with a single coat.
That number drops on textured walls, unpainted drywall, or porous surfaces like bare wood and brick. Rough textures can cut coverage down to 250-300 square feet per gallon because the paint soaks in or fills gaps.
Different paint finishes affect coverage too. Flat paint usually goes further than semi-gloss or high-gloss finishes, which have higher solids content and apply thicker.
Primer coverage runs similar to paint - around 350-400 square feet per gallon - but some stain-blocking primers cover less because they're formulated for heavy-duty sealing rather than maximum spread.
Unprimed drywall (absorbs more paint)
Textured or popcorn surfaces
Dark colors over light (or vice versa)
Porous materials like concrete and brick
Application method (spraying uses more than rolling)
Latex paint delivers standard coverage, dries fast, and works for most interior walls and ceilings.
Oil-based paint covers slightly less per gallon but provides a harder, more durable finish. Cleanup requires mineral spirits instead of water.
Specialty paints like textured coatings or high-build primers might only cover 200-250 square feet per gallon because they're thicker.
Most painting projects need two coats for even color and proper coverage.
Single-coat coverage works if you're repainting the same color over a well-maintained surface. Going from one neutral shade to a slightly different neutral? You might get away with one coat.
Drastic color changes always require multiple coats. Painting a dark wall light demands at least two coats, sometimes three. The reverse - dark over light - usually needs two coats minimum to avoid streaking.
Primer counts as your first coat. If you're working with fresh drywall, stained surfaces, or making a major color in interior design shift, primer is non-negotiable before your finish coats.
Same color touch-ups
High-quality paint with excellent hiding power
Light color over light color
Previously primed and sealed surfaces
Changing colors, covering repairs, or painting unpainted surfaces. Two coats hide imperfections and deliver uniform color saturation.
New construction with fresh drywall needs primer plus two finish coats. That's three layers total.
Primer seals porous surfaces, blocks stains, and creates a uniform base for paint adhesion.
Apply primer first, let it dry completely (usually 2-4 hours), then follow with two coats of your chosen finish paint. This is standard protocol for professional results.
Some paints claim "paint and primer in one" but they're really just thick paint. They work for minor color changes on already-painted walls, not for raw drywall or problem surfaces.
Total surface area determines your paint quantity. Wall area equals length times height for each wall, then add all walls together.
Ceiling area is length times width. Multiply those two dimensions and you've got your overhead surface area.
Subtract doors and windows from your total to get actual paintable surface. This prevents overbuying paint for areas you won't cover.
L-shaped rooms or spaces with alcoves need individual wall measurements. Measure each section separately, calculate area for each, then sum everything.
Break irregular shapes into rectangles and triangles. Calculate each geometric section using basic formulas, add them up.
Sloped ceilings require measuring the actual angled surface, not the horizontal distance. Use a laser measurer or climb up with a tape measure to get accurate diagonal measurements.
Vaulted ceilings add significant square footage. The pitch creates more surface area than a flat ceiling over the same floor space.
Standard interior doors measure approximately 20 square feet (3 feet wide by 7 feet tall). Deduct this from each wall that has a door.
Windows vary but average 15 square feet for typical residential windows. Large picture windows or bay windows need individual measurements.
Most paint calculators automatically subtract standard door and window sizes when you input the quantity of each. Manual calculations require you to multiply number of openings by their average size, then subtract from total wall area.
Count every door and window in the room. Three windows at 15 square feet each equals 45 square feet to deduct.
French doors and sliding glass doors run larger than standard doors. A standard sliding door is roughly 35-40 square feet.
Latex paint is water-based, dries in 1-2 hours, covers 350-400 square feet per gallon, and cleans up with soap and water.
Oil-based paint takes 6-8 hours to dry, covers slightly less (300-350 square feet per gallon), but creates an extremely durable finish that resists moisture and wear.
Primer coverage matches standard paint at 350-400 square feet per gallon. Stain-blocking primers cover less because they're thicker and designed to seal rather than spread.
Textured paint for accent walls or decorative finishes covers 200-250 square feet per gallon. The texture compounds add thickness that reduces spread.
High-gloss finishes apply thicker than flat paint. Expect 300-350 square feet per gallon instead of 400.
Ceiling-specific paint formulas are thicker to prevent dripping while you work overhead. Coverage runs 300-350 square feet per gallon.
Popcorn ceilings eat paint like crazy. The textured surface can drop coverage to 250 square feet per gallon or less because paint fills all those little peaks and valleys.
Smooth ceilings with standard ceiling paint cover around 350 square feet per gallon. If your ceiling measures 300 square feet, one gallon handles it with paint left over.
Measure the actual sloped surface area, not just the floor plan. A 12x15 room with a cathedral ceiling might have 250+ square feet of ceiling instead of the flat 180.
Height matters for application difficulty but doesn't change coverage rates. You'll need the same paint per square foot whether the ceiling is 8 feet or 20 feet high.
Measure linear footage of all trim, then multiply by the height of the trim piece. A room with 50 linear feet of 4-inch baseboard has roughly 17 square feet of baseboard surface.
Crown molding typically runs 3-6 inches tall. Measure the room perimeter, multiply by molding height divided by 12 to get square footage.
Door frames and window trim add up fast. Each standard door frame (including the header) is about 15 linear feet, window frames average 10-12 linear feet.
One quart of trim paint covers roughly 100 square feet, perfect for most single-room trim work.
Calculate each room separately using the room paint calculator, then add totals together. This gives you accurate paint needs for whole-house projects.
Same color throughout? Combine all room totals and buy in 5-gallon buckets for better pricing. Different colors per room require separate calculations and individual gallon purchases.
Batch your rooms by color family to minimize leftover paint. Painting three bedrooms the same shade? Calculate total square footage for all three at once.
An accent wall requires paint for only one wall instead of the entire room. Measure that single wall's length and height, multiply, subtract openings.
A typical 12-foot by 8-foot accent wall covers 96 square feet. One gallon of paint handles it with plenty to spare for touch-ups.
Different color for your focal wall? Buy separately from your main room color and calculate only that specific wall surface.
Exterior surfaces demand different coverage calculations. Siding material drastically affects paint consumption.
Wood siding covers 350-400 square feet per gallon on smooth surfaces, drops to 250-300 on rough-sawn cedar.
Brick and stucco are porous nightmares. Expect 150-250 square feet per gallon because paint soaks into the material instead of sitting on the surface.
Vinyl siding (if painting is even recommended) covers 300-350 square feet per gallon. Metal siding runs similar.
Concrete block walls might only get 150-200 square feet per gallon on the first coat. Second coat improves to 250-300 as the primer seals porosity.
Add 10% overage to your calculated paint needs. This accounts for spillage, uneven application, and future touch-ups.
Complex rooms with lots of cuts around trim, multiple corners, or unusual architectural features warrant 15% extra.
Textured walls automatically increase waste because rollers hold more paint that doesn't all transfer to the surface.
Fresh drywall needs primer before paint. Period. Drywall soaks up paint unevenly without a sealed base coat.
Stain-blocking primer covers water damage, smoke stains, or marker scribbles. One coat seals the problem so your finish paint looks clean.
Painting over dark colors? Tinted primer in a shade close to your finish color reduces the number of topcoats needed.
Standard primer covers 350-400 square feet per gallon on sealed surfaces. Raw drywall drops that to 300-350 as it absorbs more product.
Shellac-based primers for serious stain blocking cover 250-300 square feet per gallon. They're thicker but necessary for tough jobs.
Flat paint spreads furthest at 400 square feet per gallon. The matte finish has less pigment density than glossier options.
Semi-gloss covers around 350 square feet per gallon. More resin content means less coverage but better durability.
High-gloss paint is the thickest with the least coverage, typically 300-350 square feet per gallon. Perfect for trim and doors where you want that reflective finish.
Textured paint for creating patterns or dimensional effects covers 200-250 square feet per gallon depending on application thickness.
Required inputs: room length, width, ceiling height. These are non-negotiable for any calculation.
Optional inputs improve accuracy: number of doors, number of windows, number of coats, paint type, surface texture.
Measurement precision to the nearest foot works fine for most rooms. Getting within 6 inches is plenty accurate for paint estimation.
Choose feet or meters depending on your measuring tools. Most US calculators default to feet, international versions use metric.
Quart covers approximately 100 square feet. Perfect for small bathrooms, accent walls, or touch-up supplies.
Gallon covers 350-400 square feet. This is your standard single-room paint purchase.
Five-gallon bucket covers 1,750-2,000 square feet and costs less per gallon than buying five individual gallons. Smart choice for large projects or multiple rooms in the same color.
Sample sizes (half-pint or smaller) cover 15-20 square feet. These are for testing colors, not actual painting projects.
Expect ±10% variation from calculator estimates. Surface texture, application method, and painter skill all affect actual consumption.
Professional painters working with quality tools hit closer to predicted amounts. DIY first-timers often use 15-20% more paint than calculations suggest.
Textured surfaces, dramatic color changes, and porous materials push actual usage above estimates. Smooth walls with minor color shifts come in under predicted amounts.
Input paint price per gallon and the calculator multiplies by required gallons for total material cost.
Add labor costs by estimating hours and hourly rate. Most painters charge $25-$50 per hour depending on location and experience.
Total project cost includes paint, primer, supplies (rollers, brushes, tape, drop cloths), and labor if hiring help. Material costs typically run $50-$150 for a standard bedroom.
Flooring calculator for determining square footage when you're renovating floors in the same room you're painting.
Tile calculator helps estimate materials for bathroom or kitchen projects where paint meets tile work.
Wallpaper calculator for accent walls or rooms where you're mixing wallpaper with painted surfaces.
LED light requirement calculator because proper light in interior design affects how paint colors appear in the finished space.
Color theory in interior design principles help you select shades that work with your existing furniture and lighting.
The room color scheme generator suggests coordinating palettes based on your preferences and room characteristics.
Test paint samples on your actual walls before buying gallons. Colors shift dramatically based on natural light, ambient lighting, and adjacent surfaces.
Different interior design styles favor specific color palettes - Scandinavian interior design leans toward whites and neutrals while Bohemian interior design embraces rich, saturated hues.
Roller application delivers the best coverage efficiency. A 9-inch roller with proper technique achieves the 350-400 square feet per gallon standard.
Brush application uses more paint per square foot because brushes hold less product and require more dipping. Expect 10-15% more paint consumption when brush-rolling entire walls.
Spray application is fastest but wasteful. Overspray and airborne paint particles mean you'll use 20-30% more paint than roller application for the same surface area.
Bathrooms need moisture-resistant paint with mildew inhibitors. Coverage rates stay standard but product cost runs higher.
Kitchens benefit from scrubbable semi-gloss or satin finishes that handle cleaning. These finishes cover 350 square feet per gallon.
Bedrooms typically use flat or eggshell finishes that maximize coverage at 400 square feet per gallon.
Professional painters minimize waste through experience. They know exactly how much paint a roller holds and apply it efficiently.
DIY painters typically use 10-20% more paint than calculations predict. Uneven application, drips, and over-rolling waste product.
Hiring professionals costs $2-$6 per square foot including labor and materials. Doing it yourself cuts costs to $0.50-$1.50 per square foot for materials only.
Premium paints from Sherwin-Williams or Benjamin Moore offer better hiding power. One coat of premium often equals two coats of economy paint.
Budget paints require more coats to achieve uniform color. You might save $10 per gallon but end up buying twice as much paint.
Coverage rates on the can assume quality product. Discount paint might claim 400 square feet per gallon but deliver 300 in practice.
Buy 10% extra paint and keep the sealed leftover cans for future touch-ups. A quart of your wall color saves you from trying to match the shade years later.
Properly sealed paint lasts 2-3 years in storage. Write the room name and date on the can lid with permanent marker.
Small touch-ups need minimal paint. A 2-ounce sample container handles scuffs and nail holes without opening your full quart.
|
Room Type |
Dimensions (ft) |
Wall Paint (gal) |
Ceiling Paint (gal) |
Total Paint |
|---|---|---|---|---|
|
Small Bathroom |
5×8 |
0.75 |
0.5 |
1.25 gal |
|
Large Bathroom |
8×10 |
1.5 |
0.75 |
2.25 gal |
|
Small Bedroom |
10×10 |
1.5 |
1 |
2.5 gal |
|
Medium Bedroom |
12×12 |
2 |
1 |
3 gal |
|
Master Bedroom |
14×16 |
2.5 |
1.5 |
4 gal |
|
Living Room |
16×20 |
3.5 |
2 |
5.5 gal |
|
Kitchen |
10×12 |
2 |
1 |
3 gal |
|
Dining Room |
12×14 |
2.5 |
1.25 |
3.75 gal |
Assumes 8-foot ceilings and two coats on walls. Includes standard doors and windows.
|
Surface Material |
Coverage (sq ft/gal) |
Coats Needed |
Notes |
|---|---|---|---|
|
Smooth Drywall |
400 |
2 |
Best coverage rate |
|
Textured Walls |
300 |
2 |
Extra paint fills texture |
|
Bare Drywall |
350 |
2 + primer |
Always prime first |
|
Previously Painted |
375 |
1-2 |
Depends on color change |
|
Wood Paneling |
350 |
2 + primer |
Prime for best results |
|
Brick (interior) |
200 |
2-3 |
Very porous surface |
|
Concrete Block |
175 |
2-3 |
Absorbs lots of paint |
|
Popcorn Ceiling |
250 |
2 |
Texture eats paint |
|
Smooth Ceiling |
350 |
2 |
Standard coverage |
|
Opening Type |
Average Size (sq ft) |
Deduction Amount |
|---|---|---|
|
Interior Door |
20 |
Full deduction |
|
Exterior Door |
21 |
Full deduction |
|
French Doors (pair) |
40 |
Full deduction |
|
Sliding Glass Door |
35 |
Full deduction |
|
Standard Window |
15 |
Full deduction |
|
Large Window |
25 |
Full deduction |
|
Picture Window |
35 |
Full deduction |
|
Bay Window |
45 |
Full deduction |
Deduct these areas from your total wall calculations.
|
Finish Type |
Coverage (sq ft/gal) |
Best Uses |
Durability |
|---|---|---|---|
|
Flat/Matte |
400 |
Ceilings, low-traffic walls |
Low |
|
Eggshell |
375 |
Living rooms, bedrooms |
Medium |
|
Satin |
350 |
Kitchens, hallways, kids' rooms |
Medium-High |
|
Semi-Gloss |
350 |
Bathrooms, trim, doors |
High |
|
High-Gloss |
300 |
Cabinets, furniture, accent trim |
Very High |
|
Can Size |
Coverage Area |
Typical Use |
Cost Range |
|---|---|---|---|
|
Sample (8 oz) |
15-20 sq ft |
Color testing only |
$3-$5 |
|
Pint |
50 sq ft |
Touch-ups, small repairs |
$8-$15 |
|
Quart |
100 sq ft |
Bathroom, accent wall, trim |
$12-$25 |
|
Gallon |
350-400 sq ft |
Single room walls |
$25-$60 |
|
5-Gallon |
1,750-2,000 sq ft |
Multiple rooms, whole house |
$100-$250 |
Prices vary by brand and quality. Premium brands cost 30-50% more.
|
Project Complexity |
Waste Factor |
Why You Need Extra |
|---|---|---|
|
Simple repaint (same color) |
5% |
Minor touch-ups |
|
Standard room (new color) |
10% |
Spillage, uneven application |
|
Multiple rooms |
10% |
Consistent batching |
|
Textured surfaces |
15% |
Extra absorption |
|
Complex trim work |
15% |
Cutting in, detail work |
|
Dramatic color change |
15% |
Additional coats needed |
|
First-time DIY project |
20% |
Learning curve, mistakes |
Paint calculators provide ±10% accuracy when you input precise measurements. Actual paint consumption varies based on surface texture, application method, and painter experience. Textured walls, porous surfaces, and dramatic color changes typically require more paint than standard estimates predict.
Yes. Subtracting doors and windows prevents overbuying paint for areas you won't cover. Standard doors are roughly 20 square feet, windows average 15 square feet. Most calculators automatically deduct these when you input quantities, improving your paint quantity estimate accuracy.
A 12x12 room with 8-foot ceilings needs approximately 2 gallons for walls (two coats) plus 1 gallon for ceiling. Total surface area is around 384 square feet for walls. Add doors and windows into your calculation for precision before purchasing paint.
Add 10% overage to calculated amounts for spillage, uneven application, and future touch-ups. Complex rooms with extensive trim or textured surfaces warrant 15% extra. This prevents mid-project store runs and ensures you have matching paint for repairs down the road.
Exterior calculators account for porous materials like brick, stucco, and wood siding that absorb more paint. Coverage drops from 400 square feet per gallon on smooth drywall to 150-250 on brick. Exterior paint formulas also factor weather resistance and thicker application requirements.
Yes. Primer covers approximately 350-400 square feet per gallon, matching standard paint coverage. Calculate total surface area once, then determine if you need primer (fresh drywall, stain blocking, dramatic color change) before applying your finish coats for complete project planning.
Most calculators default to two coats but let you adjust. Single-coat coverage works for minor color changes over well-maintained surfaces. New construction, bare drywall, or dramatic color shifts require primer plus two finish coats, which you'll need to specify for accurate estimates.
Yes. Flat paint covers 400 square feet per gallon while semi-gloss covers 350 and high-gloss covers 300-350. Glossier finishes have higher resin content that applies thicker. Textured decorative paints cover only 200-250 square feet per gallon due to added texture compounds and application thickness.
Measure the actual sloped surface, not the horizontal floor plan. Cathedral ceilings and vaulted spaces add significant square footage beyond flat ceiling calculations. Break complex angles into triangles and rectangles, calculate each section separately, then sum the total ceiling area for accuracy.
Measure only that wall's length and height, multiply for square footage, then subtract doors or windows if present. A standard 12x8-foot accent wall is 96 square feet. One gallon easily covers it with leftovers. Calculate separately from your main room color for precise purchasing.