---
title: "Paint Calculator | Gallons, Liters & Wall Area | BQ Calculator"
canonical: "https://calculator.bqtools.com/paint-calculator/"
description: "Estimate wall paint in gallons or liters from room dimensions, doors, windows, coats, optional ceiling area and adjustable manufacturer coverage."
---

# Paint Calculator

Estimate paint for a rectangular room using wall dimensions, openings, number of coats, optional ceiling area and the coverage printed on your paint.

BQ Calculator · https://calculator.bqtools.com/paint-calculator/

## Inputs

Share links contain only the values needed to recreate this calculation.

## Paint estimate

## How this paint estimate works

The calculator finds the four-wall area of a rectangular room, subtracts approximate door and window openings, optionally adds the ceiling, multiplies by the number of coats, and divides by the paint coverage you provide.

## Formula

```text
wallArea = 2 × (length + width) × height paintableArea = wallArea - openings + optionalCeiling paintRequired = paintableArea × coats / coverage
```

All dimensions are converted internally to meters. US coverage in square feet per gallon is converted to square meters per liter before the shared calculation engine runs.

## Worked example

A 12 × 10 ft room with 8 ft walls, one standard door, two standard windows, two coats and 400 ft²/gal coverage produces a planning estimate after subtracting the assumed openings. Enable the ceiling to include another 120 ft² before coats.

## Assumptions and limitations

Actual paint usage depends on product, primer, surface texture, application method and color change. Verify the manufacturer coverage value and round purchases according to the container sizes available to you.

## Frequently asked questions

### How much area does a gallon of paint cover?

Coverage varies by product and surface. This calculator defaults to 400 square feet per US gallon, which is about 10.5 square meters per liter, and lets you replace that assumption with the coverage printed on your paint label.

### Does the calculator subtract doors and windows?

Yes. It uses approximate opening areas for each door and window count before applying the number of coats. Unusually large openings should be handled by adjusting dimensions or using the result as a planning estimate.

### Can I include the ceiling?

Yes. Enable the ceiling option to add room length multiplied by width to the paintable area before multiplying by the number of coats.

### Why might I need more paint than the estimate?

Texture, porosity, color changes, primer, application method, spillage and manufacturer-specific coverage can all increase real consumption.

### Does the can count optimize combinations of five-gallon and one-gallon containers?

No. The page shows simple upward-rounded equivalents. Purchase sizes and return policies differ, so use the raw gallon or liter requirement when choosing actual container combinations.

### Related calculators

All calculation inputs stay local to this browser.

## Machine-readable resources

- Calculator registry: https://calculator.bqtools.com/calculators.json
- Site index: https://calculator.bqtools.com/llms.txt
- Full agent text: https://calculator.bqtools.com/llms-full.txt
- Agent discovery index: https://calculator.bqtools.com/agent-index.json