How to use this calculator
- Measure each rectangular room or non-overlapping floor section. Use the same units within each input.
- Enter the actual product specifications, your chosen allowance and usable quantity already owned. Enter zero explicitly where appropriate.
- Assign rooms to product entries. Matching names alone do not combine products.
- Resolve every incomplete or invalid group. Review the quantity to buy and all assumptions.
- Take the current material's CSV or print summary. Save or back up JSON to continue editing the complete project.
A reproducible test example
31 m² of walls, two coats, 10 m²/L per coat, 10% entered allowance and 2.5 L cans → 6.82 L need and three cans to buy.
These are test inputs, not recommended product values. Use “Try the test example” to inspect them; it replaces the current project only after confirmation when edits are unsaved.
Supported scope and limitations
Rectangular rooms with explicit door/window deductions from walls. Assigned ceiling paint is separate unless it uses the same product entry. Coverage is for one coat; US liquid gallons are explicit. Primer is not automatically included.
Clearing browser storage can remove saved projects. Downloads remain in your files. No account, cloud storage or background upload is provided.
Read the detailed paint guide · Review calculation methods · Understand local storage
Sources and scope
For definitions of wallpaper match, repeat and packaging, see Brewster's product properties and Graham & Brown's wallpaper FAQ. Product instructions take precedence over generic examples. Unit conversions use the exact international foot (0.3048 m) and US liquid gallon (3.785411784 L); see NIST conversion factors.