How Much Paint for One Room? Complete Guide (2026)

Before you buy paint, the biggest question is simple: how much do you actually need? Buy too little and you'll make a second trip mid-project. Buy too much and you're stuck with half-used cans. Either way, it costs time and money.

This guide shows exactly how much paint one room requires, with formulas, room-by-room estimates, and a shortcut calculator to save you the math.

Quick Answer: 1–2 Gallons Per Room

For a standard 10×12 ft bedroom with 8-ft ceilings and one coat of paint:

Walls: ~1 gallon (covers ~350 sq ft)
Ceiling: ~1 gallon
Trim (baseboards, doors, windows): ~1 quart

Add a second coat → double the wall paint. Most painters recommend 2 coats for uniform color and durability.

The Formula (Works for Any Room)

Step 1 — Measure Wall Area

Wall area = (Length + Width) × 2 × Height

Example: (10 + 12) × 2 × 8 = 352 sq ft

Step 2 — Subtract Doors and Windows

Each door ≈ 20 sq ft. Each window ≈ 15 sq ft.

352 − 20 (door) − 15 (window) = 317 sq ft

Step 3 — Divide by Coverage

One gallon of interior paint covers ~350 sq ft per coat (check the can — cheaper paints cover less).

317 ÷ 350 = 0.9 gallons per coat

Step 4 — Multiply by Coats

Two coats: 0.9 × 2 = 1.8 gallons → buy 2 gallons.

Room-by-Room Paint Estimate

Room	Size (ft)	Wall Paint (2 coats)	Ceiling	Trim
Small bedroom	10×10	1.5 gal	1 gal	1 qt
Standard bedroom	10×12	2 gal	1 gal	1 qt
Master bedroom	12×16	2.5 gal	1 gal	1 qt
Living room	15×20	3 gal	1.5 gal	2 qt
Bathroom	5×8	1 gal	0.5 gal	1 qt
Kitchen	10×12	2 gal	1 gal	1 qt

For a precise estimate, use our Paint Calculator.

Factors That Change the Amount

Color change: Dark → light needs 2–3 coats plus primer.
Wall texture: Rough or textured walls absorb 20–30% more paint.
Wall condition: Fresh drywall or patched areas absorb extra primer and paint.
Paint quality: Premium paints cover in 1 coat; economy paints often need 3.
Ceiling height: A 10-ft ceiling instead of 8 ft adds 25% more wall area.

Should You Prime First?

Primer is required if:

Painting over bare drywall or new wood
Switching from dark to light color
Covering stains, smoke damage, or water marks
Painting over glossy surfaces

Primer covers 200–300 sq ft per gallon — budget 1 extra gallon for a standard room.

How to Save Paint (Without Cutting Quality)

Use a quality brush and roller — cheap tools waste paint.
Use a primer tinted toward your topcoat color.
Wrap rollers/brushes in plastic between coats — no washing = no waste.
Buy the right finish (eggshell for walls, satin for trim, flat for ceilings).
Keep leftover paint for touch-ups — labeled with room and date.

Common Paint Coverage (Per Gallon)

Type	Coverage
Interior wall paint (flat/matte)	350 sq ft
Interior wall paint (eggshell/satin)	400 sq ft
Primer	250 sq ft
Ceiling paint	350 sq ft
Trim/doors (semi-gloss)	350 sq ft