Paint Calculator
Estimate how much paint a room needs in gallons or liters, with cans, cost, primer, supplies, and budget-first or cans-first modes.
Room & coverage
Updates as you typeMode
What do you want to solve for? ?
Available budget
—
$
Cans already on hand
—
gal
Room preset (optional)
Room dimensions
Measurement unit
Length ?
—
ft
Width ?
—
ft
Ceiling height ?
—
ft
Surfaces to paint
Ceiling adds floor area. Trim adds ~1 ft² per perimeter foot (baseboard + crown).
Openings
Doors ?
—
count
Windows ?
—
count
Paint
Quality tier ?
Coats ?
—
coats
Can size ?
Display (optional)
Currency
Coverage per gallon ?
—
sq ft
Price per gallon
—
$
Door size ?
sq ft
Window size ?
sq ft
Primer ?
—
Primer price / gal
$
Supplies ?
$
Formula
G
=
(2·(L + W)·H − Dopenings) · C
K
- G
- Gallons needed (rounded up)
- L, W, H
- Length, width, and ceiling height
- Dopenings
- Total area subtracted for doors and windows
- C
- Number of coats
- K
- Coverage per gallon (paint-label value)
Worked example — your numbers
- Perimeter = 2·(L + W) = —
- Wall area = perimeter · H = —
- Openings subtracted = —
- Paintable area = —
- Total with coats = paintable · C = —
- Gallons = total ÷ coverage = —
Ceiling (if selected) adds L·W; trim adds roughly 1 ft² per perimeter foot (baseboard + crown combined). Primer counts the paintable area once, not once per coat.