Paint Calculator – How Much Paint Do I Need for My Room?
How much paint do I need? Our free paint calculator works it out for one wall, a whole room, or the entire house. Enter the room size, subtract doors and windows, choose the paint, the surface, the number of coats, and primer, and you get the gallons you need, the cheapest mix of quarts, gallons, and 5-gallon buckets, the total cost, and a printable shopping list with tape, drop cloths, and rollers.
How to Use the Paint Calculator
- Pick a tab. “Rooms” is for complete rooms, “Surfaces” for single walls, doors, fences, or ceilings, and “Whole home” gives a quick estimate from the floor area.
- Measure the room. Enter length, width, and wall height in feet, plus the number of doors and windows. The quick sizes fill in common rooms such as 10 × 12 or 12 × 14.
- Check the openings. A standard door counts as 3 × 6.67 ft (20 sq ft) and a window as 3 × 5 ft (15 sq ft). Change the sizes for patio doors or big windows.
- Add the ceiling if it gets the same paint. Check “Paint the ceiling too.” If the ceiling gets a different white, calculate it on the “Surfaces” tab instead.
- Choose paint, surface, and coats. The paint type sets a starting coverage, and rough or porous surfaces add extra. Two coats are standard, and primer can be added as its own coat.
- Enter your prices. The calculator tests every mix of the can sizes you select and picks the cheapest one that covers the job.
- Take the list along. Copy the shopping list, print it on US Letter or A4, or copy a share link that opens your exact values later.
How Much Paint Do I Need? The Quick Math
Every paint estimate follows the same steps, and the calculator shows each of them in the result:
- Wall area = (length + width) × 2 × wall height
- Area to paint = wall area − doors − windows (+ ceiling)
- Gallons = area to paint × coats ÷ coverage per gallon
- Add about 10% for rollers, trays, touch-ups, and the paint that stays in the can
Most interior latex wall paint covers about 350 to 400 square feet per gallon in one coat on a smooth, painted wall. The calculator starts at 400 sq ft per gallon. If your can says something else, type that number in the coverage field. It always beats any average.
Example: a 14 × 16 Bedroom
A 14 × 16 ft bedroom with 8 ft walls has a perimeter of 60 ft and 480 sq ft of wall. Minus one door (20 sq ft) and two windows (30 sq ft), 430 sq ft remain. Two coats mean 860 sq ft of painting, which is 2.15 gallons at 400 sq ft per gallon, or 2.36 gallons with 10% extra.
With the sample prices of $20 per quart and $45 per gallon, the cheapest way to buy it is two gallons plus two quarts for $130. Three gallons would cost $135 and leave more paint over.
The Same Room With the Ceiling
The ceiling adds 14 × 16 = 224 sq ft. Now 654 sq ft get two coats, which is 3.27 gallons, or 3.6 gallons with extra. Four gallons ($180) are the best buy here.
One Accent Wall
A single 12 × 8 ft wall has 96 sq ft. Two coats need 0.48 gallons, or 0.53 with extra. Two quarts would be just short, and three quarts cost more than a gallon, so the calculator suggests one gallon. Use the “Surfaces” tab for walls like this.
A Whole House From the Floor Area
With normal ceiling heights, the wall area of a home is about twice its floor area. A 1,500 sq ft home therefore has about 3,000 sq ft of walls. Two coats need 15 gallons, or 16.5 gallons with extra. With the ceilings, it is 4,500 sq ft and 24.75 gallons, which is five 5-gallon buckets. Use this only as a first budget and measure room by room before you buy.
Paint Coverage per Gallon
Coverage changes with the product, the color, and the surface. These are the starting values the calculator uses. The ranges come from data sheets of major brands.
| Paint type | Start value | Typical range |
|---|---|---|
| Interior wall paint (latex) | 400 sq ft/gal | 250 to 450 sq ft/gal |
| Enamel or trim paint | 400 sq ft/gal | 250 to 450 sq ft/gal |
| Exterior house paint | 300 sq ft/gal | 250 to 400 sq ft/gal |
| Porch and floor paint | 350 sq ft/gal | 200 to 400 sq ft/gal |
| Epoxy floor coating | 250 sq ft/gal | 125 to 250 sq ft/gal |
| Primer | 300 sq ft/gal | 200 to 400 sq ft/gal |
Brands differ more than many people expect. Our comparison of Sherwin-Williams vs. Benjamin Moore looks at coverage and hide, and acrylic vs. latex paint explains the main paint types. For outdoor jobs, see our guide to the best exterior paint.
Surface, Coats, and Primer
Why the Surface Matters
The coverage on the label assumes a smooth, sealed surface. Texture adds surface area, and porous materials soak up paint. The calculator multiplies the paint by a surface factor: 1.0 for smooth, painted walls and metal, 1.15 for textured wallpaper, 1.2 for bare wood, 1.25 for new drywall or fresh plaster, 1.3 for textured or concrete surfaces, and 1.5 for rough stucco. You see the factor right in the result.
How Many Coats?
Two coats are the norm, because the second evens out color and sheen. One coat can work when you refresh a wall in the same color with a good paint. Going from dark to light usually needs primer plus two coats. Our guide on how many coats of paint on a wall goes through each case.
When to Add Primer
Prime new drywall, bare wood, stains, and glossy old paint. Primer seals the surface so the topcoat goes further and looks even. The calculator adds one coat of primer with its own coverage (300 sq ft per gallon to start). Read primer vs. undercoat to choose the right product and how long to wait between priming and painting to plan your day. For new walls, our guide to the best drywall primer helps.
Buying the Right Cans
Interior paint comes in quarts, gallons, and 5-gallon buckets. A gallon holds four quarts, but four quarts usually cost much more than one gallon. Buckets are the cheapest per gallon for big jobs. The calculator compares all mixes of the sizes you select, so you never pay for two quarts when one gallon is cheaper. Our guide to paint can sizes explains every size from a sample can to a bucket.
A few habits save money and trouble:
- Buy all of one color at once. Tinted paint can vary slightly between batches.
- Mix the cans together. When you use several gallons on one wall, pour them into a bucket and stir, so the color stays even.
- Keep a little for touch-ups. The 10% extra is also your repair paint for later scuffs.
- Do not forget the supplies. The shopping list adds painter’s tape, plastic sheeting, a roller with an extension pole, an angled brush, and a tray.
Painting Tips That Save Paint and Time
- Prepare the walls. Clean them first (see how to clean painted walls) and fill holes, as shown in how to fill screw holes in a wall.
- Work in the right order. Ceiling first, then walls, then trim. Our article should you paint trim or walls first explains why.
- Cut in neatly. A clean edge with a brush means less tape and fewer touch-ups. See how to cut in paint.
- Plan the time. A typical bedroom takes a day with prep and two coats. Our guide on how long it takes to paint a room breaks it down step by step.
- Pick the sheen. Flat hides flaws, satin and eggshell clean better. Compare eggshell vs. satin paint.
Metric Units, Privacy, and Limits
Switch to metric to enter meters and get liters, or kilograms for floor coatings sold by weight. The calculator runs entirely in your browser, with no sign-up, and nothing you type is sent anywhere. The share link keeps your values in the part of the address after the # sign, which browsers do not send to the server.
All numbers are estimates. Real coverage depends on the paint, the color change, your roller, and the wall. The label and data sheet of your paint come first. When in doubt, paint one wall, see how much you used, and adjust the coverage in the calculator.
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Frequently Asked Questions
How Much Paint Do I Need for a Room?
Measure the perimeter, multiply by the wall height, and subtract doors and windows. Multiply by the coats and divide by the coverage on the can, about 400 sq ft per gallon. A 12 × 12 ft room with 8 ft walls usually needs about 2 gallons for two coats.
How Many Gallons of Paint Do I Need for a 14 × 16 Room?
With 8 ft walls, one door, and two windows, a 14 × 16 room has 430 sq ft to paint. Two coats need about 2.4 gallons with extra, so buy two gallons and two quarts, or three gallons. With the ceiling, plan on four gallons.
How Much Does One Gallon of Paint Cover?
One gallon of interior latex paint covers about 350 to 400 sq ft in one coat on a smooth wall, so about 200 sq ft with two coats. Rough and porous surfaces need more paint.
How Much Paint Do I Need for One Wall?
A 12 × 8 ft wall needs about half a gallon for two coats. A gallon is often cheaper than three quarts, so most people buy one gallon.
How Much Paint Do I Need for a Ceiling?
Multiply the room length by the width. A 12 × 14 ft ceiling has 168 sq ft, so two coats take about 0.9 gallons with extra. Check the coverage on your ceiling paint, because it can differ from wall paint.
How Much Paint for the Whole House Interior?
As a rough guide, the wall area is twice the floor area. A 1,500 sq ft home has about 3,000 sq ft of walls and needs about 16.5 gallons for two coats, plus more for ceilings and trim.
Should I Subtract Doors and Windows?
Subtract large openings such as patio doors and big windows. Small ones matter less, because their frames and trim also take paint. The calculator subtracts 20 sq ft per door and 15 sq ft per window by default.
Is the Paint Calculator Free?
Yes. It is free, needs no account, works in US or metric units, and lets you copy, print, or share your shopping list.
Robert Thompson has worked as a self-employed carpenter for over 15 years. He lives with his family in Billings, Montana, where he also successfully operates his business as a woodworker. His main business is the complete interior construction of buildings. He is also passionate about creating high-quality wood furniture with epoxy and other items made from burl wood. Besides the woodwork, Robert is also a skilled DIY professional for all kinds of materials. He always has a solution ready for every craft and construction challenge. Originally, Robert studied civil engineering and has advanced degrees in carpentry and business management. Robert has been working for Craft Art since 2020 and enriches the blog with his immense knowledge and skills in the field of woodworking and home improvement. He writes the articles about DIY and Repair.
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