Paint Calculator

No. This tool estimates wall area only. If you plan to paint the ceiling, add extra paint based on the ceiling square footage and your product's coverage rate.

Use Extra / waste allowance (default 0%). For typical cut-ins and touch-ups, about 5–15% is common. For rough, porous, highly absorbent, or difficult surfaces, about 10–30% extra is often more realistic—those ranges describe different job conditions, not two conflicting defaults. The calculator multiplies base volume by (1 + waste% ÷ 100). Real-world use still varies with primer, color change, and application method.

Use the coverage figure printed on your paint can when available. Interior latex often covers about 350–400 sq ft per US gallon on smooth drywall, but manufacturer labels are the best source. Switching units converts your entered coverage (US gallon ↔ liter) instead of replacing it with a different default.

US liquid gallon (exactly 3.785411784 L). Labels and conversions use US Customary volume (US gal), not the British imperial gallon.

For a rectangular room, gross wall area is 2 × (length + width) × height. Then subtract doors and windows that will not be painted. For rooms with different wall sizes, calculate each wall separately and add the areas together. This calculator can also accept gross wall area directly before subtracting openings.

For a 10 ft × 10 ft room with an 8 ft ceiling, gross wall area = 2 × (10 + 10) × 8 = 320 sq ft. At roughly 350–400 sq ft per US gallon, one coat is about 0.80–0.91 US gal before openings and waste; two coats are about 1.60–1.83 US gal. Actual need depends on doors, windows, coverage rate, coats, surface condition, and waste allowance.

For a 12 ft × 12 ft room with an 8 ft ceiling, gross wall area = 2 × (12 + 12) × 8 = 384 sq ft. At 350–400 sq ft per US gallon, one coat is about 0.96–1.10 US gal before openings and waste; two coats are about 1.92–2.19 US gal. Enter your real door/window sizes and the manufacturer coverage for a tighter estimate.

Many interior paints cover about 350–400 sq ft per US gallon for one coat on a smooth, properly prepared surface. Coverage varies with paint type, wall texture, porosity, primer, application method, and formulation. Always prefer the coverage printed on the paint can.

Coverage depends on the product. For example, paint rated at 8.5 m²/L covers about 8.5 square meters with one coat under the manufacturer's stated conditions. Use the coverage value on the container whenever it is available.

For 500 sq ft of paintable surface (not floor area): at 400 sq ft/US gal you need 1.25 US gal for one coat; at 350 sq ft/US gal about 1.43 US gal. For two coats, use net area × 2 ÷ coverage, then add waste if appropriate.

For 1,000 sq ft of paintable surface (not home floor area): at 400 sq ft/US gal you need 2.50 US gal for one coat; at 350 sq ft/US gal about 2.86 US gal. For two coats that is about 5.00–5.71 US gal before waste.

Two coats use twice the effective coverage area of one coat: paint volume = net paintable area × 2 ÷ coverage. Example: 500 sq ft net × 2 coats = 1,000 sq ft effective coverage; at 400 sq ft/US gal that is 2.5 US gal before waste.

Yes, when those openings will not be painted. Door area = height × width × count; window area = height × width × count. This calculator subtracts openings from gross wall area automatically. If a door or other surface will also be painted, estimate that surface separately.

No. Floor area and wall area are different. A 12 ft × 12 ft room has 144 sq ft of floor, but with an 8 ft ceiling the gross wall area is 2 × (12 + 12) × 8 = 384 sq ft before subtracting doors and windows. Use wall area—not floor area—for wall paint estimates.

Calculate each room separately, then add the paint volumes. If rooms use different colors, products, coverage rates, or coat counts, keep those estimates separate rather than combining all areas first—that produces a clearer shopping list.

Primer is not included in the paint-volume result. Estimate primer separately using the primer manufacturer's coverage. Primer is often useful for new or bare drywall, repairs, stains, porous surfaces, major color changes, or when the paint manufacturer requires it.

Break irregular walls into simple measurable sections, add those areas for gross wall area, then use this calculator's gross wall area mode. Enter that total before subtracting doors and windows.

Estimated cost = final paint volume × price per US gallon or liter. The calculator applies net wall area, coats, coverage, and waste first, then multiplies by the optional cost you enter. Checkout totals can differ because paint is sold in fixed container sizes.

Usually yes when buying, because paint is sold in fixed can sizes and you may want touch-up reserve. Keep the calculator's mathematical result as your planning estimate, then choose the container size that covers that volume plus any waste or spare you want on hand.

Yes, but rough, textured, porous, or highly absorbent surfaces often need more paint than smooth drywall. Prefer the manufacturer's coverage for that substrate when available, and consider a larger Extra / waste allowance—about 10–30% can be more realistic for difficult surfaces.

It is primarily for interior wall estimates. Gross wall-area mode can support a basic exterior area estimate, but exterior coverage often differs due to siding profile, masonry texture, weathering, surface condition, and exterior paint formulation. Follow the exterior product's coverage guidance.

It can. Large color changes may need extra coats, primer, or stain-blocking primer—especially going from a dark color to a light one. Set the calculator to the number of coats you actually plan to apply.

The math is accurate for the values you enter (dimensions or gross wall area, openings, coats, coverage, and waste). Real-world use can differ with texture, porosity, primer, color change, application method, spills, and leftover paint in trays or rollers. Treat the result as a planning estimate.

Gross wall area is the total wall surface before openings. Net paintable area = gross wall area − door area − window area. This calculator uses net paintable area (then multiplies by coats) to estimate how much paint the walls will actually need.