How much paint do I need for a 12 × 14 ft room with 8 ft ceilings?
For the worked example (12 × 14 ft room, 8 ft ceilings, 1 door, 2 windows) the material list is Wall paint: 2 gallons (calculated 1.95 gal, based on 375 sq ft / gal, no extra allowance). Quantities to buy are whole units rounded up from the calculated amounts. Enter your own measurements in the calculator above for your exact list.
How to use this calculator
- Measure the room length, width and ceiling height.
- Choose walls, ceiling or both, and how many coats you plan.
- Enter the number of doors and windows (open “Customize openings” if yours are an unusual size).
- Check the coverage under Assumptions against the number printed on your paint can.
- Copy, print or share the material list.
How this is calculated
- Wall area = 2 × (length + width) × height
- Paintable wall area = wall area − doors − windows
- Ceiling area = length × width
- Gallons = area × coats ÷ coverage per gallon (× extra allowance, if any)
- Buy: up to ¼ gal → 1 quart; up to 1 gal → 1 gallon; above that, the next whole gallon
Geometry is deterministic. Material coverage, density, installation waste and product yield can vary. We expose those assumptions so you can replace them with the values printed on the products you are actually buying. Treat every result as an estimate. Items on your list are labelled Calculated (straight from your measurements) or Estimated (depends on an assumption), and “Buy” quantities are whole units rounded up.
Sources
- Sherwin-Williams – Paint Calculator page. A gallon of paint typically covers about 350–400 sq ft (enough for a 10 × 10 ft room), texture and coverage can change how much you use; primer is described at roughly 200–300 sq ft per gallon. Basis for the 375 sq ft/gal wall and ceiling default (middle of the published range) and the 300 sq ft/gal primer default. This site is not affiliated with Sherwin-Williams. Your paint can’s coverage always takes precedence.
Last reviewed: . See the methodology.
Assumptions
These starting values are used until you change them. They are typical, not universal. Check the label on the product you are buying.
| Assumption | Starting value | Where it comes from |
|---|---|---|
| Quart purchase rule | ≤ ¼ gal → 1 quart · ≤ 1 gal → 1 gallon · above → next whole gallon | Common planning default – US purchase logic. In metric mode there is no package rule: the result is the minimum volume, rounded up to 0.1 L. Container sizes vary by market and manufacturer. |
| Paint coverage | 375 sq ft / gal | Manufacturer / industry sourced |
| Ceiling paint coverage | 375 sq ft / gal | Manufacturer / industry sourced |
| Primer coats | 1 | Common planning default |
| Primer coverage | 300 sq ft / gal | Manufacturer / industry sourced |
| Extra allowance | 0% | Common planning default |
Worked example
A 12 × 14 ft room with 8 ft ceilings, one standard door (3 × 7 ft) and two standard windows (3 × 5 ft), painted with two coats at 375 sq ft per gallon:
- Wall paint: 2 gallons (365 sq ft to cover, 2 coats) · 375 sq ft / gal, no extra allowance
Common questions
Why does the calculator show two numbers?
The math (for example 1.95 gallons) is what the geometry and coverage produce. You cannot buy 1.95 gallons, so the material list rounds up to a purchasable quantity.
Does it add waste to paint?
Not by default. Coverage is already an approximation, so the extra allowance starts at 0%. Add a cushion under Assumptions if you want one.
Should I trust the 375 sq ft per gallon default?
Treat it as a starting value. Coverage depends on the product, surface texture and application method, so replace it with the number on your paint can.
Do I need to count small windows and doors?
Subtracting them gives a closer estimate. For a very small difference you can enter 0 and accept a slightly higher paint quantity.
Guides
- How Much Paint Do I Need for a Room?Wall area, coats and coverage turned into gallons to buy.
- How Much Paint Do I Need for a Ceiling?Ceiling area, coats and coverage, with the quart-versus-gallon cut-off.
- Should You Subtract Doors and Windows When Painting?When deducting openings changes the paint you buy, and when it does not.
- How Many Sheets of Drywall Do I Need?Wall and ceiling area divided by sheet size, with waste and rounding.
- How to Measure a Room for a Material EstimateFloor, wall and ceiling area from a tape measure and a sketch.