Understanding your result
The headline is the accent colour for the coats the colour depth needs (or the coats you chose), with the allowance, and the sub-line adds the cans of tinted primer when the depth calls for it. The three figures show the paintable area, the coats, and the primer quantity or “not needed”.
The breakdown lists the wall area, the openings, the colour depth with its recommendation, the usual coverage, coats and allowance lines, and then the tinted primer and the sample pots as their own rows. The shopping list at the bottom puts all three products together.
One wall is a small quantity, and the rounding is a large share of it. A dark 14 × 8 ft wall needs 1.01 gallons: a gallon alone is just short, so the result says a gallon and a quart. If the colour is a stock colour you can buy later, the gallon and a careful hand will do; if it is a custom mix, buy the quart, because a second batch mixed a month later will not match. The other three walls belong to the wall paint calculator, and the coats calculator applies the same colour-depth rules to any surface.
How we calculate this
The colour-depth rule follows what the manufacturers say about their deep bases: light and medium colours are mixed in white or pastel bases with plenty of hiding pigment and cover in two coats; dark and saturated colours are mixed in deep, ultra-deep or clear bases with little white in them and need a third coat, or a tinted primer, to hide a light wall. The guide to dark colours and LRV explains the light reflectance value behind the depth classes, and the coverage rates table lists the coverage figures for deep-base paints, which are often lower than the 350 default; change the coverage if your can says so.
The primer is costed at 300 sq ft per gallon, the figure high-hide primers print for previously painted walls, and it is always one coat. The primer calculator does the same arithmetic for a whole room and other surfaces. Sample pots are counted rather than calculated: the quantity in a pot is tiny, and what you are buying is the chance to see the colour on the wall before committing a gallon, which the sample pot calculator turns into patches and cost.
The assumptions behind the numbers
| Assumption | Default | Where it comes from |
|---|---|---|
| Coverage per coat | 350 sq ft per gallon | Interior wall paint data sheets (Sherwin-Williams, Benjamin Moore, Behr): 350–400 sq ft per gallon; deep bases often quote the low end |
| Coats, light and medium | 2 | Manufacturers’ recommendation for a colour change |
| Coats, dark and very dark | 3 | Manufacturers’ guidance for deep and ultra-deep bases over a lighter colour, or 2 over a tinted primer |
| Tinted primer coverage | 300 sq ft per gallon | High-hide primer data sheets (Kilz, Zinsser, Sherwin-Williams) for previously painted walls |
| Sample pot | 8 fl oz, about 10 sq ft at two coats | Standard sample size at US paint stores; 8 fl oz is 1/16 gallon, which at 350 sq ft per gallon covers about 22 sq ft once or 11 twice |
| Allowance | 5% | Roller loss and a touch-up jar |
Assumptions last reviewed October 7, 2026.
The calculator does not model a change from a very dark wall back to a light colour, which is the primer’s job (choose “dark colour going light” in the primer calculator), or bare drywall, which needs its own primer first. The primer guide covers both, and the coats guide has the full table of colour and sheen changes.
Two worked examples
A navy wall behind the bed
A 14 × 8 ft wall with no openings, going from white to navy, two colours still being considered.
- Area: 14 × 8 = 112 sq ft
- Depth: dark, so 3 coats and a tinted primer
- Per coat: 112 ÷ 350 = 0.32 gallons
- Needed: 0.32 × 3 × 1.05 = 1.01 gallons, buy 1 gallon + 1 quart
- Tinted primer: 112 ÷ 300 × 1.05 = 1.57 quarts, buy 2 quarts
- Sample pots: 2
With the primer, two finish coats would probably do, and the gallon alone would cover them with a little over. The calculator keeps the three-coat recommendation because the third coat is the safe assumption; the primer is what makes it possible to stop at two.
A deep red dining-room wall
A 16 × 9 ft wall in a saturated red, three colours to test.
- Area: 16 × 9 = 144 sq ft
- Depth: very dark or saturated, so 3 coats and a grey-tinted primer
- Per coat: 144 ÷ 350 = 0.411 gallons
- Needed: 0.411 × 3 × 1.05 = 1.3 gallons, buy 1 gallon + 2 quarts
- Tinted primer: 144 ÷ 300 × 1.05 = 2.02 quarts, buy 3 quarts (or a gallon)
- Sample pots: 3
Reds are mixed in clear bases and are the worst coverers in the store; a grey primer is standard practice under them. The same wall in a pale colour, with a 15 sq ft window taken out, would need 2.33 quarts for two coats and no primer at all.
Where to find your inputs
Width and height. Tape measure along the baseboard and up the corner. A wall with a sloping ceiling: measure the average height, or the area from a plan.
Openings. A window is about 15 sq ft, a door 20, a fireplace opening around 10 to 15 with the hearth excluded. Built-ins that are not being painted count too.
Colour depth. The paint chip usually says the base (“deep base”, “ultra-deep”, “clear”) or the light reflectance value. Under about LRV 20 is dark; under 10, or any saturated red, orange or yellow, is very dark. The LRV guide has a table.
Coverage. From the can. Deep-base paints often say 300 to 350 rather than 400.
Common mistakes
- Buying one gallon for a dark wall and running out on coat three. Three coats of 112 sq ft is 336 sq ft; a gallon at 350 has no allowance at all.
- Skipping the tinted primer to save money. It costs less than the finish paint it replaces and gives a more even colour.
- Painting the accent wall first. Do the light walls first and cut the dark colour in against them.
- Judging the colour from the chip. A 2 × 2 ft patch on the wall, two coats, seen morning and evening, is the only honest test.
- Mixing the leftover into another can. Keep the accent colour sealed on its own for touch-ups.
- Using the same sheen as the light walls without thinking. Dark colours show roller texture; a flat or matt finish hides it, an eggshell shows it.
Questions people ask
- How much paint does an accent wall take?
- A 14 × 8 ft wall is 112 sq ft. In a dark colour at three coats and 350 sq ft per gallon that is 1.01 gallons with the allowance, so a gallon and a quart. In a light colour at two coats, the same wall with a window takes 2.33 quarts, so three quarts.
- Do dark colours really need three coats?
- Over a light wall, usually yes, because the deep-base paint they are mixed in has less white pigment and hides less per coat. The alternative is two coats over a primer tinted toward the finish colour, which costs less than the third coat of a deep-base paint and is what the calculator recommends for dark and very dark colours.
- What is tinted primer?
- Ordinary primer that the store adds colourant to so it is grey or a muted version of your finish colour. It gives the first finish coat a darker base to cover, which is why one coat of it replaces a whole coat of the expensive paint. Ask for it at the paint counter; most stores tint primer free.
- How many sample pots do I need?
- One per colour you are seriously considering, and no more than three or four or the decision gets harder. An 8 fl oz pot covers about a 2 × 2 ft patch at two coats, which is enough to judge the colour in morning and evening light on the actual wall.
- Should I paint the accent wall first or last?
- Last. Paint the three light walls first, let them dry, then tape the corners and do the accent wall, so the dark colour is cut in against finished light walls where a slip is easy to hide with the light colour. Cutting a light colour against a dark edge shows every wobble.
- Why does the leftover matter here?
- Because the accent colour is the one you will need for touch-ups and the one you are least likely to have. The result rounds the quantity to cans and shows the leftover; keep the sealed quart rather than mixing it into the main batch.