BuildMaterialCalc

Paint & Finishes

How Much Paint Do I Need?

Quick Reference

At a glance

Approximate gallons needed by room size (2 coats, 8 ft ceiling)
RoomWall areaWalls onlyWalls + ceiling
10 × 10 bedroom320 ft²2 gal2 gal
12 × 14 bedroom416 ft²3 gal3 gal
16 × 20 living room576 ft²4 gal4 gal
Open concept (40 × 20)960 ft²6 gal8 gal
Whole interior (1,500 ft² home)4,800 ft²28 gal36 gal

How to calculate it yourself

Gallons = ceil((wall_area − doors − windows) × coats ÷ 350). Doors ≈ 21 ft². Windows ≈ 15 ft². For two coats, multiply by 2 before dividing.

Common scenarios

Bedroom refresh (12×12, 8' ceiling)

Walls: 384 ft² − 1 door − 1 window = ~348 ft². Two coats = 696 ft² ÷ 350 ≈ 2 gallons.

Whole-room makeover with primer

Add 1 gallon of primer to the 2 gallons of color. Use primer when going from dark to light or covering stains.

Exterior siding (1,500 ft² home)

Exterior typically needs 6–8 gallons because siding texture absorbs more paint. Always two coats.

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Related questions

Frequently asked

  • A standard 12×12 bedroom with 8 ft ceilings needs 2 gallons for two coats on the walls. Add a third gallon if you're also painting the ceiling.

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About this calculation

Written and maintained by the BuildMaterialCalc editorial team. The math is derived from published codes and manufacturer specs — see our methodology page for the full source list and review process.

Last reviewed: 9 May 2026. We update cost references quarterly using the Bureau of Labor Statistics Producer Price Index plus regional supplier spot-checks.

Every result is an estimate. Real-world projects vary with sub-grade conditions, ambient humidity, supplier spec sheets, and local code amendments. For structural, code, or safety-critical applications, confirm with a licensed professional. See our full disclaimer for details.