Skip to main content
Builder.Tools
ToolsPricingFind a BuilderFor TradespeopleBlog
UKUS
Builder.Tools

Practical construction calculators and project tools. 5 tools stay free; the full quotes, jobs and invoices workspace is localized for UK firms.

Tools

  • Calculators
  • AI-Powered
  • Utilities

Company

  • Find a Builder
  • Join Our Network
  • Trade Partners
  • For US Contractors
  • Our Story
  • Blog
  • Help & Support
  • Contact

Legal

  • Terms of Service
  • Privacy Policy
  • Cancellation & Refunds
  • Disclaimer
  • Affiliate Disclosure

© 2026 Builder Tools. All rights reserved.

Need a hand? Help & Support · contact@builder.tools

Built in the UK. Now building for US contractors too.

  1. Home
  2. Tools
  3. Paint

Paint Calculator

Calculate how much paint you need for any room. Accounts for doors, windows, coats, and tin sizes.

How to use the Paint Calculator

  1. Enter the room dimensions — length, width, and height.
  2. Specify the number and size of doors and windows to deduct.
  3. Select the paint type and number of coats.
  4. Review the total litres needed and the number of tins to buy.

Why use this tool

  • Deducts doors and windows from the paintable area for an accurate calculation.
  • Accounts for multiple coats — most paints need two coats for proper coverage and colour depth.
  • Converts litres into standard tin sizes so you know exactly what to buy.

Paint coverage varies by product, but a typical matt emulsion covers approximately 12-14 square metres per litre on a smooth, sealed surface. The first coat on bare plaster absorbs significantly more — up to 50% more — so a mist coat (diluted emulsion) is recommended first. This calculator uses standard coverage rates for each paint type and adjusts for the number of coats. It deducts doors and windows from the total wall and ceiling area so you do not over-order. When in doubt, round up to the next tin size — having a small amount left over for touch-ups is always useful.

Part of Builder Tools Calculators — free construction tools for UK tradespeople.

Related building tools

  • Cable Lookup
  • Concrete
  • VAT & CIS

What are you working on?

The calculation stays the same. The output changes to suit the job.

Choose your view
Paint Calculator

Calculate how much paint you need for a room based on dimensions, openings, and coverage.

Most emulsion covers 10–14 m²/litre. Check the tin.

Results

Tins Needed

3 × 2.5Ltins

Total Litres Needed

5.1L

Paintable Area

30.3m²

Calculation results
Wall area33.6m²
Ceiling area12m²
Deductions (doors + windows)3.3m²
Paintable area30.3m²
Coats2
Total coverage needed60.6m²
Litres needed5.1L
Tins needed3 × 2.5L

Coverage varies by surface type, colour, and application method. Porous or textured surfaces may need more paint.

Dark colours over light surfaces typically need an extra coat.

Ready to price

Check the measured quantities, add your rates below, then send them to a quote.