Quick rule: wall area is room perimeter × wall height, minus doors and windows. Multiply by the number of coats, add 10% for application loss and touch-ups, then divide by the paint's stated coverage.

Paint-by-room-size reference chart

The figures below are exact planning quantities before rounding to locally available containers. A lower coverage rate produces a more conservative estimate. Download the data as a CSV file for a worksheet, article, or project brief.

Paint needed by room size chart for one and two coats — Planning gallons for common room sizes at one and two coats. The detailed table below includes both 350 and 400 sq ft per gallon scenarios.

Room	Net walls	1 coat		2 coats
Room	Net walls	350 ft²/gal	400 ft²/gal	350 ft²/gal	400 ft²/gal
10×10 ft	269 ft²	0.85 gal	0.74 gal	1.69 gal	1.48 gal
10×12 ft	301 ft²	0.95 gal	0.83 gal	1.89 gal	1.66 gal
12×12 ft	333 ft²	1.05 gal	0.92 gal	2.09 gal	1.83 gal
12×14 ft	365 ft²	1.15 gal	1.00 gal	2.29 gal	2.01 gal
14×16 ft	429 ft²	1.35 gal	1.18 gal	2.70 gal	2.36 gal

Shared assumptions: rectangular room, 8-foot walls, one 21 ft² door, two 15 ft² windows, smooth previously painted walls, no ceiling, and 10% extra. Paint trim and primer separately. Always replace the planning coverage with the figure on the selected product's label.

Net wall area = 2 × (length + width) × height − doors − windowsGallons = net wall area × coats × 1.10 ÷ coverage per gallon

Paint estimates for common room sizes

Room and project	Net wall area	Calculated paint	Plan to buy
10×10 room · 2 coats	269 sq ft	1.69 gal	2 gallons
10×12 room · 2 coats	301 sq ft	1.89 gal	2 gallons
12×12 room · 2 coats	333 sq ft	2.09 gal	3 gallons
12×14 room · 2 coats	365 sq ft	2.29 gal	3 gallons
14×16 room · 2 coats	429 sq ft	2.70 gal	3 gallons
10×10 room · 1 coat	269 sq ft	0.85 gal	1 gallon
12×12 room · 1 coat	333 sq ft	1.05 gal	2 gallons
12×12 room · 2 coats + ceiling	333 sq ft + 144 sq ft ceiling	3.00 gal	3 gallons
12×14 room · 2 coats + ceiling	365 sq ft + 168 sq ft ceiling	3.35 gal	4 gallons
10×12 room · 2 coats	345 sq ft	2.17 gal	3 gallons

These examples assume 8-foot walls unless the link says otherwise, one standard door, two standard windows, 350 sq ft of coverage per gallon, and 10% extra. Container recommendations are planning quantities—not a guarantee of actual consumption.

Choose the closest room, then customize it

10×10 room · 2 coats 10×12 room · 2 coats 12×12 room · 2 coats 12×14 room · 2 coats 14×16 room · 2 coats 10×10 room · 1 coat 12×12 room · 1 coat 12×12 room · 2 coats + ceiling 12×14 room · 2 coats + ceiling 10×12 room · 2 coats

Why the same room can need more paint

Porous or textured walls: effective coverage may be lower than the number on the can.
A dramatic color change: an additional coat or tinted primer may be needed.
Tall walls and ceilings: every extra surface adds area to every coat.
Spraying: overspray can increase material use compared with rolling.

Measure before purchasing

A room-size page is useful for an early budget, but field measurements should determine the final purchase. Measure unusual doors, large windows, closets, alcoves, and sloped surfaces separately. Use the custom paint calculator when your room differs from these examples.

Sources and methodology

The 350–400 ft² per gallon range is a general smooth-wall planning range, not a universal product claim. It is consistent with guidance published by major paint manufacturers. See the full calculator methodology and the following primary references:

When citing this table, link to this page so readers can inspect the assumptions and use a custom calculation. Last reviewed: September 9, 2026.