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Paint Calculator

Estimate how much paint your walls need, including multiple coats.

Your numbers

Make it your own
Updates as you type
Whole containers to buy
4US gal

Calculated from your inputs · rounded for display

Paint needed4US gal
Paintable area700ft²
Estimated paint cost$160.00

Coverage is user supplied. Surface texture, primer, color change, and product instructions affect actual consumption.

Your calculation, step by step

No black boxes
  1. Net area = 800 − 100 = 700.
  2. Paint needed = 700 × 2 ÷ 350 = 4.
  3. Round up to 4 one-gallon containers.

What if things were different?

Save up to three scenarios, then change your inputs to compare the possibilities.

How to use this calculator

  1. Enter your own values in the labeled fields. Check the units and assumptions before comparing results. Only the fields needed for your selected calculation mode are shown.
  2. Your answer updates automatically. Review the calculation steps to see exactly how it was calculated.
  3. Copy, share, save, or download your result. Saved inputs stay on this device.

How the calculation works

Paint needed = (wall area − openings) × coats / coverage

Subtract doors and windows from the wall area, multiply by the number of coats, and divide by product coverage. Use the label coverage for your paint and surface. The purchase estimate rounds up to one-gallon or one-liter containers; other container sizes require separate adjustment.

A worked example

(800 − 100) ft² × 2 coats ÷ 350 ft²/gal = 4 US gallons.

Reading your result

Use the main result together with its units and supporting figures. Display values are rounded; calculations keep their underlying precision. A change in inputs or assumptions can change the answer. Compare the step-by-step working with your intended use before relying on an estimate.

Frequently asked questions

Is primer included?

No. Calculate primer separately using its coverage and coat count.

Why can the real requirement differ?

Porosity, texture, application method, and color change affect coverage.

Sources & methodology

This calculator uses the mathematical identity and assumptions stated above. No current rates, prices, or external data are loaded. Conversion tools use international unit definitions.

Formula review: October 24, 2026. Read our methodology.