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Professional painters estimate quantities in minutes. This guide teaches the calculation so you buy exactly what you need.
The Formula
Area = Width × Height × Number of walls | Litres = Area × Coats ÷ 10 (coverage per litre)
Standard formula used by professionals worldwide
Worked Example
Step-by-step
Bedroom 4m × 3m, 4 walls × 2.5m height = 40m² | 2 coats → 40×2÷10 = 8L + 10% = 9L
Key Concepts
- Accuracy: Results are as accurate as the inputs you provide
- Units: Always use consistent units throughout your calculation
- Verification: Double-check important calculations before making decisions
- Professional advice: For major financial, health, or structural decisions, consult a qualified professional
Privacy and Security
- All calculations run entirely in your browser
- No data is sent to any server
- No sign-up or personal information required
- Your data stays private — always
Frequently Asked Questions
Include doors and windows in area?
Subtract 2m² per door and 1m² per window for a practical estimate.
Coats needed?
2 for most walls. 3 for dramatic colour changes or bare plaster.
Order of painting?
Ceiling first, then walls top to bottom, then woodwork and skirting last.