Short answer: the coverage number is printed on the can, usually as a range such as 350–400 sq ft per gallon. Type the number from your can into the calculator. Do not use a website default, including ours.
How many square feet does a quart of paint cover?
A quart is a quarter of a gallon, so it covers a quarter of what your can claims — and then you divide again by the coats you are actually putting on. At a 400 figure that is 100 sq ft in one coat, which is where the quoted “a quart covers 100 square feet” comes from, and 45.5 sq ft once the same wall is getting two coats and a 10% allowance.
| Coverage on the label | A quart, 1 coat, no allowance | A quart, 2 coats + 10% | A gallon, 2 coats + 10% |
|---|---|---|---|
| 250 sq ft/gal | 62.5 sq ft | 28.4 sq ft | 113.6 sq ft |
| 350 sq ft/gal | 87.5 sq ft | 39.8 sq ft | 159.1 sq ft |
| 400 sq ft/gal | 100.0 sq ft | 45.5 sq ft | 181.8 sq ft |
| 450 sq ft/gal | 112.5 sq ft | 51.1 sq ft | 204.5 sq ft |
Figures rounded to a tenth of a square foot. Sherwin-Williams publishes both halves of this on its calculator page: “A gallon of paint typically covers about 350-400 square feet” and “A quart of paint covers 100 square feet” (read 2026-09-09). The 100 is not wrong, and it is not the number you shop with either: it is the top of that gallon range, at one coat, with nothing set aside. Plan a two-coat wall at 100 sq ft to the quart and you will buy a little under half of what you need. The read-off table from 100 to 1,000 sq ft of wall is in wall square feet to paint cans.
Where to find it on the can
Look on the back or side label for “coverage”, “covers up to” or “spread rate”. It is given per gallon (or per quart on small cans) and often comes with a condition such as “on smooth, sealed surfaces”. If the label gives a range, the lower number is the safer input for a porous or textured wall.
Why it is a range, not a constant
Two examples from one manufacturer’s technical data sheets: Regal Select Interior (550) lists “Coverage per Gallon at Recommended Film Thickness 400 – 450 Sq. Ft. … Depending on surface texture and porosity” (data sheet, US, 2018), and Ultra Spec 500 Interior Eggshell (N538) lists 350 – 400 sq. ft. with the same caveat (data sheet, US, 2019). Different products, finishes and walls give different numbers. These are dated examples of how a data sheet reads, not current product claims; the can you buy is the source of truth.
Same room, two coverage numbers
A 12 ft × 10 ft room with 8 ft walls and 20 sq ft of openings has 332 sq ft to paint. With two coats and a 10% allowance:
| Coverage on the label | Paint the math needs | What you buy (gallons + quarts) | Left over from rounding |
|---|---|---|---|
| 350 sq ft/gal | 2.087 gal | 2 one-gallon cans + 1 quart (2.25 gal) | 0.163 gal |
| 400 sq ft/gal | 1.826 gal | 2 one-gallon cans (2 gal) | 0.174 gal |
Fifty square feet per gallon on the label changed the shopping list by one quart. That is why the calculator asks for your label instead of assuming one.
Keep area and coats apart
Two coats on 332 sq ft is 664 “coat-square-feet” of paint work, but the wall did not get bigger. The calculator shows the wall area once and multiplies by coats in the formula. Same room at 350 sq ft/gal: one coat needs 1.043 gal (1 one-gallon can + 1 quart); two coats need 2.087 gal (2 one-gallon cans + 1 quart). Follow the coat count on the can for your surface; new drywall usually needs two.
Primer and finish are separate products
Primer has its own coverage and its own coats. Run the calculator once per product you will buy; do not add a primer coat to the finish-paint calculation.
When 2.01 gallons becomes “2 gallons + 1 quart”
Cans come in fixed sizes, so the calculator rounds up to the next can it can buy. The rounding depends on which can sizes you tell it are available. Examples at 1 coat, 100 sq ft/gal, no allowance (so the gallons equal the square feet ÷ 100):
| Area to paint | Paint the math needs | Gallons + quarts available | Gallons only |
|---|---|---|---|
| 200 sq ft | 2.00 gal | 2 gal | 2 gal |
| 201 sq ft | 2.01 gal | 2 gal + 1 qt (2.25 gal) | 3 gal |
| 225 sq ft | 2.25 gal | 2 gal + 1 qt (2.25 gal) | 3 gal |
| 226 sq ft | 2.26 gal | 2 gal + 2 qt (2.5 gal) | 3 gal |
| 300 sq ft | 3.00 gal | 3 gal | 3 gal |
| 301 sq ft | 3.01 gal | 3 gal + 1 qt (3.25 gal) | 4 gal |
One extra square foot past a whole gallon adds a quart; if only gallon cans are sold, it adds a whole gallon. The calculator rounds by volume, not by price: two quarts may cost more than a gallon at your store, and a slightly larger allowance may push you over a boundary. Check the boundary before you choose the allowance.
Questions people ask
The label says “up to 400 sq ft”. Which number do I type?
“Up to” is the best case. Use a lower number if your wall is unpainted drywall, patched, textured or a darker color change; the label itself usually says the coverage is lower on porous surfaces.
Do I subtract windows and doors?
Only the openings you actually measured (width × height of each). The calculator has a field for that; leaving it at 0 simply buys a little more paint.
Does the quart price matter?
Not to this calculator. It gives the smallest purchase volume that covers the math. Compare prices at the store.
Rooms where this number decided the order
Six worked examples that turn on the figure printed on the can.
- Your floor area is not your wall area — a 400-square-foot floor sits under anywhere from 640 to 1,360 square feet of wall, and only the wall number belongs in a calculator.
- The two ends of a printed range are two shopping lists — a 14-by-16 living room comes to 4 gallons plus 2 quarts at one end of the ranges manufacturers print, and 2 gallons plus 3 quarts at the other.
- When the can size beats the label — on a 5-by-8 bathroom every figure from 250 to 450 square feet a gallon lands on one gallon plus a quart or less, so whether the shop sells quarts decides one can or two.
- One maker, four products, two coverage numbers — the same company publishes 350–400 on one wall paint and 400–450 on another, and its own calculator tells you it has already assumed two coats and left the ceiling out.
- Wall square feet to paint cans — a read-off table from 100 to 1,000 square feet of wall at four label coverages, and the quart-sized steps that decide which side of a boundary you land on.
- Primer is a separate can — a primer prints 200 to 300 square feet a gallon against 350 to 400 for a finish, and on one wall that makes a single primer coat the same purchase as two finish coats.
Every table on this page was checked against the site’s calculation code and its automated tests on 2026-10-19, when the quart table was added; the other two were first checked on 2026-09-08. They describe the examples shown, not any specific product.
Sources: Benjamin Moore Regal Select 550 TDS; Benjamin Moore Ultra Spec 500 N538 TDS; Sherwin-Williams paint calculator FAQ (read 2026-09-09). Arithmetic: this site’s calculator, see how Wall Math calculates.