Understanding your result
The headline is the cost of the cheapest combination, and the sub-line names the cans and the leftover. The three figures show the cans, the paint bought and the leftover. The bars compare the cheapest mix with each single-size option and with the site’s standard rounding.
The table gives the paint needed, the cheapest combination, its cost, the paint bought and the leftover, then each alternative with its cans and cost, and finally the price per gallon or litre of each size so you can see which is the bargain. The note says how much the cheapest mix saves against the dearest option.
Run this after any quantity calculator and before the store. The paint cost calculator prices a quantity with the standard rounding, supplies and tax; the quantity converter turns a litre figure into gallons or the reverse; the leftover planner handles what is left; and the whole-house estimator gives the quantities for each product on a large job, where the savings are largest.
How we calculate this
The search is exhaustive: for each number of pails from none to enough on their own, each number of gallons that could follow, the quarts that close the gap are counted, and every combination’s cost is compared. With three US sizes and a few gallons of paint there are only a few dozen combinations; with four metric sizes and large quantities, a few thousand, which the browser does instantly. The answer is therefore the cheapest possible at the prices you entered, not a rule of thumb.
The site’s standard rounding, which every quantity calculator uses, is quarts up to a gallon, gallons up to four, and a pail once the remainder passes four gallons; in metric, 10, 5, 2.5 and 1 litre cans. It is shown as an alternative so you can see when it is the cheapest (often) and when it is not. The can sizes page lists the sizes and the can sizes guide explains the buying maths.
The assumptions behind the numbers
| Assumption | Default | Where it comes from |
|---|---|---|
| Pail | $185 for 5 gallons | Typical 2025 US home-improvement price for a mid-range wall paint pail |
| Gallon | $40 | The same line by the gallon |
| Quart | $16 | The same line by the quart |
| Metric prices | 75 / 42 / 24 / 12 per 10 / 5 / 2.5 / 1 L | Illustrative; enter your local prices |
| US sizes | 5 gal, 1 gal, 1 qt | Standard US retail sizes |
| Metric sizes | 10, 5, 2.5, 1 L | Common European and Canadian sizes |
Assumptions last reviewed October 8, 2026.
The calculator does not know about multi-buy offers, contractor discounts or the cost of a second trip to the store, and it treats the quantity you enter as exact. Enter the quantity before rounding, including the allowance, as the quantity calculators report it.
Two worked examples
One large room, 4.2 gallons
Pail $185, gallon $40, quart $16.
- Cheapest: 4 gallons + 1 quart = 4 × $40 + $16 = $176, 0.2 quarts left over
- A pail: $185, 3.2 quarts left over; five gallons: $200; seventeen quarts: $272
- The standard rounding buys the pail, so the cheapest mix saves $9 and a near-gallon of leftover
At 11.3 gallons the standard rounding is also the cheapest: 2 pails, a gallon and 2 quarts for $442, against $480 in gallons alone.
A metric job, 16 litres
10 L at 75, 5 L at 42, 2.5 L at 24, 1 L at 12.
- Cheapest: 10 L + 5 L + 1 L = 129, nothing left over
- Two 10 L cans: 150; four 5 L cans: 168
And a small top-up: 0.6 gallons at the US prices is one gallon for $40 rather than three quarts for $48, because three quarts cost more than the gallon that holds them.
Where to find your inputs
Paint needed. From any quantity calculator on this site, before rounding, allowance included.
Prices. From the store’s shelf or website, for the same product line, sheen and base. Deep bases sometimes cost more than pastel ones.
Sizes not sold. Leave them blank.
Common mistakes
- Comparing prices across product lines. Compare sizes of the same line and sheen.
- Rounding before entering the quantity. Enter the exact figure and let the search round.
- Buying the pail for 4.2 gallons by reflex. Check the gallons-and-quarts mix.
- Three quarts instead of a gallon. Almost always dearer.
- Not boxing several cans of a tinted colour. Pour them together for an even colour.
- Forgetting the touch-up quart. If the cheapest mix leaves nothing over, that may be a reason to round up.
Questions people ask
- Is a 5-gallon pail cheaper than five gallons?
- Per gallon, usually by 10 to 20%. At $185 for a pail against $40 a gallon, the pail is $37 a gallon. But if you need 4.2 gallons, four gallons and a quart at $176 is cheaper than the pail and leaves almost nothing over. The calculator checks every combination.
- When is a pail the best buy?
- When you need more than about four and a half gallons of one colour, or when the job is large enough that several pails and a few gallons cover it. On a whole house the pails save real money; on one room they mostly buy leftover.
- Are quarts worth it?
- For topping up, yes. Quarts cost roughly 40% more per gallon than gallons, but a quart that avoids a second gallon is cheaper. Three quarts usually cost more than a gallon, which is why the calculator often swaps three quarts for one gallon.
- What sizes does it use in metric?
- 10, 5, 2.5 and 1 litre cans, the common European and Canadian sizes. Enter the price of each size your store sells and leave the others blank.
- What if my store does not sell a size?
- Leave its price blank or zero and the calculator ignores it. With only gallons and quarts priced it finds the best mix of those two.
- Will the cans match in colour?
- Tinted paint from different cans can differ slightly. If you buy several cans of one colour, pour them together in a large bucket and stir before you start, which painters call boxing. It matters more with deep colours.