Free paint calculator for any room. Enter your measurements and get instant results - gallons needed, cost estimates, and coverage area. ✨
Enter your room dimensions to get started
Tell us about doors, windows, and paint coats
Our free paint calculator tells you exactly how much paint to buy for any room in seconds. Simply measure your space, enter the dimensions, and get instant results showing gallons needed, square feet coverage, and cost estimates. No confusing formulas, no guesswork, no wasted trips to the hardware store.
This paint calculator by square foot accounts for doors, windows, multiple coats, and uses realistic coverage numbers (350 sq ft per gallon, not the optimistic 400 sq ft manufacturers claim). Whether you're using Sherwin Williams, Behr, Benjamin Moore, or any paint brand, this paint room calculator gives you accurate results for bedrooms, living rooms, kitchens, bathrooms, or entire houses.
Step 1: Calculate wall area = (Length × Height × 2) + (Width × Height × 2)
Step 2: Subtract doors (21 sq ft each) and windows (15 sq ft each)
Step 3: Divide by 350 sq ft (realistic coverage per gallon)
Step 4: Multiply by number of coats needed
Or just use our paint calculator above and skip the math! 🎯
To calculate paint by square foot: divide your total wall area by 350 (realistic coverage per gallon). For example, a 12×15 room with 8ft ceilings has about 432 sq ft of wall space, requiring 1.2 gallons per coat, or 3 gallons total for 2 coats.
Use our calculator above for instant results without manual math.
Our room paint calculator handles any room size. Just enter length, width, and ceiling height. The calculator automatically accounts for standard doors and windows, giving you accurate paint quantities for bedrooms, living rooms, kitchens, or bathrooms.
Works for rooms from 10×10 to 20×30 and beyond.
This door paint calculator subtracts door area (average 21 sq ft per door) and window area (average 15 sq ft per window) from your total. This prevents overbuying paint and saves money. Simply count your doors and windows when using the calculator.
Automatically calculated - no manual deductions needed.
New drywall needs primer before paint. This drywall primer calculator uses the same square foot formula but typically requires only 1 coat. Use primer for bare drywall, patched areas, or when covering dark colors with light paint.
Primer coverage: ~350 sq ft per gallon, same as paint.
"You want to determine how many gallons of paint you need to buy to paint your bedroom. There are 4 walls in your room. Each wall is 12 feet by 15 feet. You have 2 windows and 1 door. The area of each window is 15 square feet and the door is 20 square feet. Each gallon of paint covers 400 square feet. How many gallons do you need?"
4 walls × (12 ft × 15 ft) = 4 × 180 sq ft = 720 square feet
(Note: This assumes walls, but typically it would be 2 walls at 12ft and 2 at 15ft height)
Windows: 2 × 15 sq ft = 30 sq ft
Door: 1 × 20 sq ft = 20 sq ft
Total to subtract: 30 + 20 = 50 square feet
720 sq ft - 50 sq ft = 670 square feet to paint
670 sq ft ÷ 400 sq ft per gallon = 1.675 gallons
Rounded up: 2 gallons (if store only sells whole gallons)
While the homework problem says 400 sq ft/gallon, real paint covers 300-350 sq ft in actual use. Using our paint calculator with realistic numbers: you'd need 2-3 gallons for proper coverage with 2 coats. Always buy extra for touch-ups!
Get accurate paint estimates in 4 simple steps. No guesswork, no waste, no running out mid-project. ✨
Grab a tape measure and get the length, width, and ceiling height in feet. Don't include baseboards or crown molding - just basic wall-to-wall measurements.
Walk around the room and count doors and windows. Each door saves about 21 sq ft, each window about 15 sq ft - the paint calculator subtracts these automatically.
Most paint jobs need 2 coats. Going from dark to light? Pick 3 coats. The paint calculator adjusts the total gallons based on your choice.
Click "Calculate Paint Needed" and instantly see gallons required, paintable area, and cost estimates for budget, quality, and premium paint.
See exactly how any paint color will look in your actual room before you buy a single gallon.
🎨Try Colors on Your Walls→Avoid costly mistakes and get professional results with these insider secrets from painting pros. 🎯
Whatever the paint calculator tells you, buy one extra gallon. You'll need it for touch-ups, and custom colors can't be perfectly matched later. That $40 now saves you from repainting an entire wall in six months.
💰Money-saving tip: Most hardware stores accept returns on unopened paint cans, so extra gallons aren't a risk.
Cheap paint ($20-25/gallon) seems like a deal until you need 3 coats and it still looks streaky. Quality paint ($35-45/gallon) covers better, lasts longer, and often needs fewer coats. The paint calculator shows costs for all quality levels - do the math on coverage vs. price.
🏆Recommended brands: Behr Premium Plus, Sherwin-Williams Duration, Benjamin Moore Regal Select
That perfect "warm gray" on the paint chip might look blue, purple, or brown on your actual walls. Lighting changes everything. Before using the paint calculator to buy gallons, test colors in your actual room with your actual lighting.
Better option:
Upload a photo of your room and see any color on your walls instantly - way easier than buying sample pots.
See the transformation: Before vs After painting
The paint calculator tells you how much paint to buy, but it can't make your walls smooth. Fill holes, sand rough spots, clean walls, and tape edges before opening a paint can. Good prep makes average paint look great. Bad prep makes expensive paint look terrible.
The paint calculator assumes painted walls. If you're painting new drywall, covering dark colors, or painting over stains, you need primer first. Don't trust "paint + primer in one" marketing - real primer is a separate product.
⚠️Need primer if: Bare drywall, dark-to-light color change, stains or water damage, porous surfaces like wood or plaster
Proper room preparation with paint supplies ready
Paint cans claim one gallon covers 400 square feet. That's true under perfect lab conditions with perfectly smooth walls and professional application. In your actual house? You're getting 300-350 sq ft per gallon. Our paint calculator uses 350 sq ft, which is realistic for most homes.
Wall texture: Rough or textured walls use 20-30% more paint than smooth walls
Paint color: Dark colors and bold shades often need extra coats for even coverage
Application method: Spraying uses more paint than rolling; rolling uses more than brushing
Surface porosity: Unpainted drywall, wood, or plaster soaks up extra paint
Paint quality: Cheap paint has less pigment and needs more coats
If your walls are textured, porous, or you're painting a bold color, add 20% more to what the paint calculator recommends. Better to have extra than to run out mid-project with no way to match the color perfectly.
Living rooms usually have large windows and multiple doors. The paint calculator automatically subtracts these, but measure carefully - that big picture window saves you half a gallon.
Tip: Use eggshell or satin finish for easy cleaning in high-traffic areas
Bedrooms typically have fewer windows and doors. Use the paint calculator as-is, but consider an accent wall to add personality without painting the entire room.
Tip: Flat or matte finish hides wall imperfections and creates a cozy feel
Kitchens have cabinets, appliances, and tile backsplashes that reduce paintable area. The paint calculator handles doors and windows, but you'll likely need less than calculated due to cabinets.
Tip: Use semi-gloss or satin for easy cleaning of cooking splatters
Bathrooms are small but humid. The paint calculator gives accurate results for area, but invest in moisture-resistant paint to prevent mold and peeling.
Tip: Semi-gloss finish resists moisture and cleans easily
Used the paint calculator and know how much you need?
Now see exactly what any color looks like in your room with your lighting and furniture. Upload a photo and try thousands of colors instantly.
Visualize Paint Colors Free →Works with any paint brand • See results in 30 seconds • No signup required
The paint calculator asks for number of coats - don't skip this! One coat almost never looks good. Budget for two coats minimum, three if going from dark to light.
This paint calculator is for walls only. Ceilings need separate calculation: length × width ÷ 350 = gallons needed. Most standard rooms need 1-2 gallons for the ceiling.
Paint cans say 400 sq ft per gallon. Real world is 300-350 sq ft. Always use a paint calculator with realistic numbers, not marketing claims from paint manufacturers.
Don't use the paint calculator to buy 5 gallons of a color you've never seen on your walls. Test first - either with sample pots or by visualizing digitally. Colors look completely different in your actual lighting.
Whatever the paint calculator says, add one gallon. You'll need it for inevitable touch-ups, and custom colors can't be matched perfectly later. That extra gallon will save you from repainting entire walls.
Get answers to the most common questions about using our paint calculator and painting your room. 🎨
You used the paint calculator and know exactly how much to buy. But do you know if that color actually works in your room?
See any paint color on your walls before buying gallons. Upload a room photo and try thousands of colors instantly. Way easier than buying sample pots and painting test squares.
Try Paint Colors Free →Free forever • No signup • See results in 30 seconds
