Calculators · 04 of 05

Paint Coverage Calculator.

Enter each wall's length and height. Set your paint's coverage rate and number of coats. The calculator figures out how many gallons you need and subtracts doors and windows if you want.

  • Imperial & metric
  • Door/window deductions
  • Multi-wall entry
  • Price estimate

The formula

How paint coverage is calculated

Add up the wall area, subtract doors and windows, multiply by the number of coats, then divide by the paint's coverage rate (sq ft per gallon).

  1. Measure walls

    Enter the length and height of each wall. The calculator multiplies them to get wall area.

  2. Subtract openings

    Enter the number of doors and windows. The calculator deducts standard opening sizes (21 sq ft per door, 15 sq ft per window). You can override those defaults.

  3. Set coverage rate

    Check your paint can. Most interior latex covers 350 to 400 sq ft per gallon. The calculator defaults to 350.

  4. Choose coats

    One coat for touch-ups, two for a color change. The calculator multiplies net area by the number of coats before dividing by coverage.

Worked examples

Three rooms, gallons calculated

Wall area minus openings, times coats, divided by coverage. Every room follows the same steps.

Example 01

A 12 × 10 ft bedroom, 8 ft ceilings

Four walls, one door, two windows. Coverage rate: 400 sq ft/gal. Two coats.

Walk-through

Walls: 2(12×8) + 2(10×8) = 352 sq ft
Openings: 1(21) + 2(15) = 51 sq ft
Net: 352 - 51 = 301 sq ft
Paint: (301 × 2) ÷ 400 = 1.51 gal

Result 2 gallons (round up from 1.51)

Example 02

A long hallway

Two walls at 20 × 9 ft, two ends at 4 × 9 ft. No windows, one door. Coverage: 350 sq ft/gal. Two coats.

Walk-through

Walls: 2(20×9) + 2(4×9) = 432 sq ft
Openings: 1(21) = 21 sq ft
Net: 432 - 21 = 411 sq ft
Paint: (411 × 2) ÷ 350 = 2.35 gal

Result 3 gallons (round up from 2.35)

Example 03

An accent wall, one coat

One wall, 14 × 9 ft. No doors or windows on this wall. High-pigment paint at 300 sq ft/gal. One coat.

Walk-through

Wall: 14 × 9 = 126 sq ft
Paint: (126 × 1) ÷ 300 = 0.42 gal

Result 1 gallon (round up from 0.42)

When you'd use this

Five reasons to calculate paint coverage

Getting the quantity right before you buy saves time and trips to the store.

  • Interior repaints

    Calculate gallons for a bedroom, bathroom, or living room before heading to the paint store.

  • Color changes

    Switching from dark to light (or the reverse) usually means more coats. Adjust the coat count and see how it changes the total.

  • Contractor estimates

    A paint quantity tied to measured wall area is more credible than a guess. Use the calculator to back up a bid.

  • Exterior painting

    Works for outside walls too. Exterior paints typically cover 250 to 350 sq ft per gallon, and textured surfaces need more paint. Adjust the coverage rate accordingly.

  • Budget planning

    Enter the price per gallon and multiply by the gallon count to get a material cost estimate.

Conversion reference

Paint coverage rates for common paint types. Check your can for the actual rate.
Paint type Coverage (sq ft/gal) Coverage (m²/L)
Interior flat/matte 350–400 8.6–9.8
Interior eggshell 350–400 8.6–9.8
Interior semi-gloss 300–350 7.4–8.6
Exterior flat 250–350 6.1–8.6
Exterior semi-gloss 250–300 6.1–7.4
Primer/sealer 200–300 4.9–7.4

Frequently asked

Paint coverage questions

The questions that come up when estimating paint quantities.

How much area does a gallon of paint cover?
Most interior latex paints cover 350 to 400 sq ft per gallon on smooth surfaces with one coat. Check the label on your specific paint. High-build or textured paints cover less.
Should I round up to the next gallon?
Yes. Paint stores sell in gallons and quarts. If the calculator says 1.51 gallons, buy 2 gallons. You will want the extra for touch-ups after furniture moves or nail holes get patched.
How do I account for textured walls?
Textured surfaces absorb more paint. Reduce the coverage rate by 10 to 25 percent. For example, if the can says 400 sq ft/gal, enter 300 to 350 in the calculator.
How do I calculate ceiling paint separately?
Use the square footage calculator to find the ceiling area (length × width of the room). Then divide that area by the paint's coverage rate and multiply by the number of coats. Ceiling paint is often a different product with a different coverage rate.