Paint Coverage Calculator
Calculate how much paint you need for your room. Estimate gallons and quarts based on room dimensions and coverage.
This calculator adds up wall area and ceiling area -- floor area is deliberately left out of Total Area to Paint, though it is still computed and shown as its own Floor Area output for reference -- then multiplies by Number of Coats and divides by Coverage per Gallon to get Gallons Needed (also shown as Quarts Needed for smaller jobs), rounding up to Gallons to Buy. Wall Area comes from twice the sum of Room Length and Room Width, times Ceiling Height, and whether Ceiling Height or Room Length swings Gallons Needed more depends on the room's proportions, not a fixed rule: Ceiling Height only outweighs Room Length when twice the Ceiling Height exceeds Room Length. Coverage per Gallon moves Gallons Needed the opposite direction from every other input here -- a paint that covers more square feet per gallon means less paint is needed for the same room, so raising this field lowers the result rather than raising it. Number of Coats scales Gallons Needed directly: two coats roughly doubles the paint needed for the same walls compared to one. This calculator has no upper bound on room dimensions or coverage rate, so it will happily size a warehouse as easily as a bedroom; it does not subtract door and window openings from wall area, so treat Gallons to Buy as a slight overestimate for rooms with a lot of glazing or oversized doors.
Inputs
Results
Total Area to Paint
472 sq ft
≈ 11 king-size beds
Gallons Needed
2.7 gal
≈ 3 milk jugs
Gallons to Buy
3 gal
≈ 3 milk jugs
How to Use This Calculator
- Enter the room length, width, and ceiling height in feet.
- Set the coverage per gallon from the paint label (typically 350–400 sq ft per gallon).
- Enter the number of coats — 2 is standard for most interior paints.
- Read the total area to paint (walls + ceiling), exact gallons (or quarts) needed, and gallons to buy rounded up.
How the result changes with Ceiling Height
| Ceiling Height | Total Area to Paint | Gallons Needed | Gallons to Buy |
|---|---|---|---|
| 3.2 | 260.8 sq ft | 1.49 gal | 2 gal |
| 11 | 604 sq ft | 3.45 gal | 4 gal |
| 21 | 1,044 sq ft | 5.97 gal | 6 gal |
| 29 | 1,396 sq ft | 7.98 gal | 8 gal |
What each input means
- Room Length
- Length of the room
- Room Width
- Width of the room
- Ceiling Height
- Height from floor to ceiling
- Coverage per Gallon
- Square feet covered per gallon (typically 350-400)
- Number of Coats
- How many coats of paint
What each result means
- Floor Area
- Shown for reference only -- not included in Total Area to Paint.
- Quarts Needed
- Gallons Needed expressed in quarts, for small jobs that don't need a full gallon.
How this is calculated
Formula
Gallons = (Total Area × Coats) / Coverage per GallonWorked example, using the default values
- Identify Input Parameters4 parametersRoom Length = 12, Room Width = 10, Ceiling Height = 8, Coverage per Gallon = 350 = 5 input(s) provided
- Calculate Total Area to PaintTotal Area to Paint472 = 472
- Calculate Gallons NeededGallons Needed2.697142857142857 = 2.697142857142857
- Calculate Gallons to BuyGallons to Buy3 = 3
- Calculate Wall AreaWall Area352 = 352
- Calculate Ceiling AreaCeiling Area120 = 120
Engine last updated .
Frequently Asked Questions
Why is floor area left out of Total Area to Paint?
Total Area to Paint only adds Wall Area and Ceiling Area together -- Floor Area is computed and shown separately (see the Floor Area output) but never included in the paint total, since most interior painting jobs cover walls and ceiling, not flooring.
Does ceiling height matter more than the room's length or width?
It depends on the room's proportions, not a fixed "yes" -- Ceiling Height only outweighs Room Length when twice the Ceiling Height exceeds Room Length. For this calculator's own default room (12 x 10 ft at 8 ft ceilings), that condition holds and Ceiling Height does move Gallons Needed more. But for a longer, more typical room -- a 20 x 10 ft room at the same 8 ft ceiling, where twice the height (16 ft) is less than the 20 ft length -- Room Length actually swings Gallons Needed by more than an equivalent percentage change to Ceiling Height. Check your own room's numbers rather than assuming either dimension always wins.
Why does raising Coverage per Gallon lower the amount of paint needed?
Coverage per Gallon is the square footage one gallon spreads across, so a higher number means each gallon covers more wall -- fewer gallons are needed for the same total area, which is why this is the one input that moves Gallons Needed in the opposite direction from all the others.
Does this calculator account for doors and windows?
No -- Wall Area is computed from the room's full perimeter and height with no deduction for door or window openings, so Gallons to Buy runs slightly high for rooms with a lot of glazing or oversized doorways. Treat the result as a conservative estimate.
Related Calculators
The questions that sit next to this one — chosen by subject, including calculators filed under a different category.
Commercial Paint Estimator
Estimate paint quantities, primer, labor hours, and costs for commercial painting projects with door and window deductions.
Construction & Building TradesPaint Calculator
Calculate how many gallons of paint you need for a room. Accounts for doors, windows, and multiple coats.
Construction & Building TradesSquare Footage Calculator
Calculate the square footage of a rectangular area. Convert between square feet, yards, and meters. Estimate total cost based on price per square foot.
Industrial CoatingElectrostatic Spray Calculator
Calculate electrostatic spray coating coverage, transfer efficiency savings, and cost comparison vs conventional spray.
Construction & Building TradesHome Project Calculator
Comprehensive home improvement calculator for paint, flooring, tile, drywall, concrete, roofing, deck, and fence projects. Get material quantities, labor estimates, and shopping lists.
More in Construction & Building Trades.