Paint Calculator – Gallons & Liters per Room

The paint calculator multiplies net wall area (perimeter × height, minus doors and windows) by your coat count, then divides by the practical coverage rate: 350-400 ft² (33-37 m²) per US gallon, or 10-12 m² per liter for typical interior emulsion. Textured or bare surfaces drop coverage to about 8 m² per liter, so prime first. Worked example: a 4 × 4 m room with 2.7 m ceilings has about 43 m² of wall; deduct 6 m² of openings and divide by 11 m²/L × 2 coats to get roughly 7 liters - two 4 L cans with touch-up left over. Always buy from one batch number: colors shift slightly between production runs, and that mismatch shows at the wall.

1. 1

   Take dimensions

   Note the room dimensions, openings and coats for the area you are covering or filling.

2. 2

   Run the calculation

   The calculator applies Gallons = (Net Area × Coats) ÷ 350; Liters = m² ÷ 10-12 per coat the moment you type.

3. 3

   Check the breakdown

   Compare base quantity and waste-adjusted totals side by side.

4. 4

   Plan the purchase

   Use the final figure to price and schedule the delivery.

• Buying exact liters

• Skipping primer

• Mismatched batch numbers