Paint coverage calculator
Sometimes you already know the square footage (painter quote, floor-plan CAD, or a careful tape job) and you only need the coverage division. Sometimes you have two leftover gallons and want to know if they finish the guest room. This page is the coverage arithmetic without forcing a full room rebuild — though you can still enter L/W/H if you want.
+10% so you don't come up short
Estimate only — not a contractor bid. Confirm bag yields and local codes before you pour or order.
When to use
Leftover paint planning; comparing 300 vs 400 sq ft/gal claims; converting a painter’s “1200 sq ft walls” note into cans.
When not to
If you have not measured openings yet, the paint calculator reduces that error.
Assumptions
User-supplied sq ft is already net of openings unless they enter room mode. Coats multiply. Waste default 10%. Coverage default 350 sq ft/gal.
Worked examples
Example 1
800 sq ft net walls, 2 coats, 350 sq ft/gal, 10% waste
→ 800×2×1.1/350 ≈ 6 gallons
Example 2
2.0 gallons on hand, 350 coverage, 2 coats
→ ≈ 350 sq ft of wall finished (2×350/2)
“On hand” assumes the paint is the right sheen and batch.
How it calculates
Enter net paintable square feet, coats, and coverage; ceil to gallons.
- Paste or type net wall area.
- Set coats and sq ft per gallon from the label.
- Add waste; buy the rounded gallon count.
gallons = ceil(sqft × coats × (1 + waste) / coverage) Reverse: sqft_covered ≈ gallons × coverage / coats
Common traps
- Coverage is per coat, not for the whole job at two coats.
- Porous new drywall drinks primer and first coat.
- Tint batches — finishing a wall from two different cans of the “same” color can flash.
Next tool
Room wizard → paint calculator.
Natural-language entry → how much paint.
FAQ
350 sq ft/gal per coat is a safe planning default on smooth interior walls.
Related
Estimate only — not a contractor bid or engineered takeoff. Confirm bag yields and local codes before you pour or order.