Paint Estimator
Calculate paint or wallpaper needed
Quick Facts
- •1 gallon covers ~350 sq ft
- •Most rooms need 2 coats
- •Buy 10% extra for touch-ups
How to Estimate Paint Needed
Calculate total wall area (2 × (length + width) × height), subtract doors (~21 sq ft each) and windows (~15 sq ft each), then divide by coverage per gallon (typically 350 sq ft). Multiply by number of coats. Dark colors over light may need 3 coats; same-color refreshes may need only 1.
Choosing Paint
Flat/matte finish hides imperfections but is harder to clean — best for ceilings and low-traffic areas. Eggshell and satin are good all-purpose finishes. Semi-gloss is ideal for kitchens, bathrooms, and trim. Always buy 10% extra for touch-ups.
Understanding the paint estimator
Paint coverage on the tin assumes a smooth, primed, mid-colour surface. Real walls have texture, absorbency, and colour changes that push actual consumption 10 to 40 percent higher. Estimating well means measuring the area properly and then applying an honest allowance.
Worked examples
Paint needed for a 4 m by 3 m room with 2.4 m ceilings
- 1Perimeter = 2 × (4 + 3) = 14 m.
- 2Wall area = 14 × 2.4 = 33.6 sq m.
- 3Subtract one door (1.9 sq m) and two windows (1.4 sq m each): 33.6 - 4.7 = 28.9 sq m.
- 4Two coats: 28.9 × 2 = 57.8 sq m of coverage needed.
- 5At 12 sq m per litre, that is 4.8 litres.
Buy 5 litres, or a 5 litre tin plus a small tester for touch-ups.
Covering a dark wall with a light colour
- 1Start with a tinted primer coat, which prevents the old colour bleeding through.
- 2Plan for three coats total rather than two.
- 3Increase the estimate by 50 percent over the two coat figure.
The 4.8 litre estimate becomes about 7.2 litres plus primer.
Coverage by surface and paint type
| Surface | Litres per coat per 10 sq m | Notes |
|---|---|---|
| Smooth primed plaster | 0.8 L | Best case, matches the tin |
| New bare plaster | 1.2 L | Needs a thinned mist coat first |
| Textured or artexed | 1.3 L | Roller nap 15 mm or more |
| Bare wood | 1.4 L | Prime knots first |
| Exterior masonry | 1.7 L | Highly absorbent |
| Ceiling (matt) | 0.9 L | Cutting in adds waste |
Standard deductions
| Feature | Area to subtract |
|---|---|
| Interior door | 1.9 sq m |
| Standard window | 1.4 sq m |
| Patio door | 3.5 sq m |
| Fireplace opening | 1.0 sq m |
Only deduct features larger than about 1 sq m. Smaller ones are cancelled out by the extra paint used cutting around them.
Frequently asked questions
More Home & Setup Fit Tools
This calculator is for educational and reference purposes only. Always verify critical calculations independently.