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Paint Calculator

Estimate paint liters and cost from wall area, opening deductions, coats, adjustable product coverage and a wastage allowance.

Calculate your quantities

Runs in your browser

Results update as you edit. Use decimal points without commas. Costs use the same currency as your entered price.

Total opening area across all walls, deducted once.

Area covered by one liter for one coat. Use the product's stated coverage; 10 is only an editable starting example.

Adds 0–100% to the calculated quantity before purchase rounding.

Optional. Use your own currency; costs exclude taxes and delivery. Zero means free, while blank leaves cost uncalculated.

Your estimate

Estimate updated. Estimated paint including wastage: 7.920 L.

Gross wall area
40.0000m²
Gross wall area (imperial)
430.5564ft²
Net paintable area
36.0000m²
Net paintable area (imperial)
387.5008ft²
Paint before wastage
7.200L
Estimated paint including wastage
7.920L
Estimated total cost
Not calculatedEnter the optional price to estimate cost

Display values are rounded; calculations and costs use unrounded quantities. Tile and box counts always round up. A “<” result is positive but smaller than the displayed decimal precision.

How to use Paint Calculator

Estimate paint for walls of the same length and height, after deducting the combined area of doors and windows. Coats multiply the paint requirement; coverage determines how much area one liter covers in one coat. Replace the starting coverage with the value stated for your paint and surface.

  1. Enter the measured dimensions and choose the unit beside each measurement. Quantities and counts must be positive whole numbers.
  2. Adjust any wastage and coverage inputs to match your estimate. Leave optional prices blank if you only need quantities.
  3. Review the results and assumptions below. Copy results includes labels and units; Reset defaults restores the starting example.

Calculation explanation

Formulas

  • Gross area = wall length × wall height × number of walls
  • Net paintable area = gross area − total door/window deduction
  • Paint before wastage (L) = net area × coats ÷ coverage per liter
  • Paint including wastage = base paint × (1 + wastage / 100)
  • Estimated cost = unrounded paint quantity × price per liter

Assumptions and measurement notes

  • The wall count assumes identical wall dimensions. For different wall sizes, calculate them separately and combine the quantities.
  • Deductions are the total across all walls and cannot exceed gross area. Coats and wall counts must be positive whole numbers.
  • Coverage varies with the product, surface and application. Paint volume is not rounded up to can sizes; choose available pack sizes when purchasing.

Units are normalized before calculation: 1 in = 0.0254 m, 1 ft = 0.3048 m, 1 ft² = 0.09290304 m² and 1 ft³ = 0.028316846592 m³. Decimal arithmetic is retained through quantity rounding; dimensions and prices are limited to 1,000,000,000 per input.

Practical examples

Four room walls

Input
4 m × 2.5 m × 4 walls; deduct 4 m²; 2 coats; 10 m²/L; 10% wastage; 12 per L
Result
Gross wall area: 40.0000 m²; Net paintable area: 36.0000 m²; Estimated paint including wastage: 7.920 L; Estimated total cost: 95.04 currency units

The net area is 36 m². Two coats need 7.2 L before allowance, or 7.92 L after adding 10%.

Three walls measured in feet

Input
12 ft × 8 ft × 3 walls; deduct 24 ft²; 2 coats; 100 ft²/L; 5% wastage; 20 per L
Result
Gross wall area (imperial): 288.0000 ft²; Net paintable area (imperial): 264.0000 ft²; Estimated paint including wastage: 5.544 L; Estimated total cost: 110.88 currency units

264 ft² of net area needs 5.28 L for two coats at the entered coverage, increasing to 5.544 L with wastage.

One feature wall

Input
5 m × 3 m; 1 wall; no deductions; 1 coat; 12 m²/L; 0% wastage
Result
Net paintable area: 15.0000 m²; Estimated paint including wastage: 1.250 L

A 15 m² wall divided by 12 m² per liter requires 1.25 L for one coat, before any packaging decisions.

Frequently asked questions

How do I find the correct coverage per liter for my paint?

Coverage varies by paint formulation and surface porosity. Smooth interior drywall with emulsion typically covers 10–14 m² (110–150 ft²) per liter per coat, whereas rough exterior masonry or unprimed plaster may cover only 4–7 m² per liter. Check the coverage rate stated on your paint can label.

Why is the estimated paint volume not rounded up to whole cans?

Paint manufacturers supply paint in multiple container sizes (such as 1 L, 4 L, 10 L, or 20 L containers, or 1 quart and 1 gallon cans). The calculator provides exact net volume including your chosen wastage allowance so you can decide the most economical container combination.

How should I calculate rooms with walls of different dimensions?

The wall count assumes identical wall dimensions. If room walls have different lengths or ceiling heights, calculate each wall separately and combine the quantities, or enter the total room perimeter as the length with a wall count of 1.

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