Wall Area
0sq ft net
0 sq ft gross, minus 0 sq ft of doors & windows.
Quick Start
Load a sample room
Pick the room closest to yours, then adjust dimensions, openings, and material settings below.
Step 1
Room dimensions & openings
Measure wall to wall. Count every door and window you plan to skip over — forgetting them is the #1 reason people overbuy.
ft
ft
ft
Subtracts 21 sq ft each.
Subtracts 15 sq ft each.
Step 2
Material settings
Paint settings
sq ft/gal
Most wall paints cover 350–400 sq ft per gallon.
When in doubt, plan for two.
Rough and porous surfaces soak up more paint.
Step 3
Get your shopping numbers
Results also update automatically as you type. Saving keeps your inputs on this device only — nothing is sent anywhere.
Results
Your material numbers
Total Paint Needed
0gallons
2 coat(s) over 0 sq ft adjusted area (surface + 10% waste).
Notes & Warnings
This tool provides estimates only — actual coverage varies by surface texture, porosity, brand, and application method. Check your product label and buy from the same dye lot (wallpaper) or color batch (paint) when possible.
Plain English
Why we do the math this way
Shopping Day
Your shopping checklist
Generated from your current inputs with real quantities. One trip, no mid-project hardware store runs.
Gear
Recommended Tools & Supplies
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Learn
The beginner’s guide to paint & wallpaper estimating
How to Calculate Paint Coverage Like a Pro
Pros follow the same sequence this calculator automates:
- Measure every wall. Add the wall lengths (or use (length + width) × 2 for a rectangular room), then multiply by ceiling height for gross wall area.
- Subtract the openings. About 21 sq ft per standard door and 15 sq ft per standard window.
- Multiply by coats. Two coats is the standard assumption; ceilings count too if you are doing them.
- Adjust for the surface. Texture and raw drywall drink more paint — budget 15–20% extra.
- Divide by coverage and add waste. Check the can’s sq ft per gallon, then keep about 10% in reserve for spills, absorption, and touch-ups.
The result rounded up to the nearest half gallon is what you buy. Keeping the receipt with a same-batch note makes topping up painless if you misjudge.
Why You Should Never Skip Primer on New Drywall
New drywall and joint compound are extremely porous and absorb paint unevenly — the result of skipping primer is a patchy finish with visible “flashing” where mud was applied, plus you end up using more expensive topcoat to get coverage. Primer seals the surface, evens out absorption, improves adhesion, and gives the finish coat a uniform base. It is equally valuable over stains, repairs, and dramatic color changes. One coat of primer is cheap insurance for a professional-looking result.
Understanding Wallpaper Pattern Repeats and Waste
Wallpaper is sold by the roll but hung by the strip. Your room’s perimeter divided by the roll width tells you how many strips you need; the roll length divided by your cut length tells you how many strips each roll yields. The catch is the cut length: wall height, plus one full pattern repeat for matching, plus about 6 inches of trim allowance at top and bottom. Random-match papers (repeat = 0) are the most economical; large geometric or floral repeats can add a third of a strip of pure waste per drop. Buy all rolls from the same dye lot, and keep one spare roll for future repairs.
The Best Roller Naps for Different Wall Textures
The nap (fuzz thickness) of a roller cover controls how much paint it holds and how it presses paint into a surface:
- 3/16″–1/4″ nap: smooth walls, doors, and cabinets — thin, even coats.
- 3/8″ nap: the all-purpose choice for smooth to lightly textured drywall.
- 1/2″ nap: orange-peel texture and lightly rough surfaces.
- 3/4″–1-1/4″ nap: stucco, brick, and heavy texture — holds a lot of paint.
Match nap to texture and you will use less paint, avoid splatter, and get a more even finish.
How to Prep Walls for a Flawless Paint Job
- Clean first. Wash walls with TSP or a degreaser, especially kitchens and baths; paint does not stick to grime.
- Patch and sand. Fill holes and cracks, sand smooth, and wipe away dust. Pre-1978 homes: test for lead before sanding.
- Tape smart. Use quality painter’s tape on trim and ceilings, press edges down firmly, and remove tape while paint is slightly tacky.
- Prime problem spots. Repairs, stains, and bare drywall all benefit from primer before the finish coat.
- Protect the room. Canvas drop cloths beat plastic — they grip the floor, absorb drips, and are not slippery.
FAQ
Frequently asked questions
How much area does a gallon of paint cover?
Most wall paints cover roughly 350 to 400 square feet per gallon for one coat. Textured, porous, or unprimed surfaces absorb more and reduce coverage, while smooth sealed walls can stretch a little further. Always check the coverage figure printed on your specific can.
Do I need to subtract windows and doors when calculating paint?
Yes, for an accurate number. A standard door is about 21 square feet and a standard window about 15 square feet. Subtracting them prevents overbuying, and a sensible waste factor still covers spills, roller absorption, and touch-ups. In very small rooms with few openings, some painters skip the deduction and treat it as built-in waste.
How many coats of paint do I actually need?
Two coats is the standard for most repaints and color changes. One coat may be acceptable when repainting with a very similar color over a sound surface, and going from a dark color to a light one can take two or three coats, often helped by a tinted primer. When in doubt, plan for two.
What is a “pattern repeat” in wallpaper?
The pattern repeat is the vertical distance before the wallpaper design starts over again. When you hang consecutive strips, the pattern must match at the seams, so you cut each strip with extra length to line it up. Larger repeats mean more trimmed-off waste, which is why large-pattern papers commonly need a 20 percent waste allowance instead of 15.
Can I paint over dark colors with just one coat?
Rarely. Dark colors tend to show through a single coat of lighter paint. The reliable approach is a high-hiding primer, sometimes tinted toward the new color, followed by two finish coats. Some premium one-coat products improve the odds, but dramatic color changes almost always need more.
How do I calculate linear feet for baseboards and trim?
Measure each run of baseboard along the walls and add them together, then add the casing around doors if you are painting that too. For paint quantity, multiply linear feet by the visible face height — roughly half a foot for a typical baseboard — then estimate coats like any other surface. This calculator does that automatically when you enable trim.
Do I need special paint for bathrooms and kitchens?
Yes, it is a good idea. Look for paints labeled for baths or kitchens, which resist moisture, mildew, and scrubbing. Semi-gloss or satin sheens hold up better than flat finishes in humid rooms, and good ventilation extends the life of any paint job.
How long does paint last in the can?
Unopened latex paint typically lasts several years, often up to about 10, when stored away from freezing temperatures. Opened cans last roughly 2 to 5 years if resealed tightly. If the paint smells rancid, has a skin that will not mix back in, or looks curdled, replace it. Dispose of old paint through local hazardous-waste or recycling programs.
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