# Paint Coverage Calculator

Calculate how many gallons of paint you need. Enter wall area, number of coats, and coverage rate. Subtract doors and windows automatically.

## What this calculates

Save money and avoid extra trips to the store by calculating exactly how much paint you need before starting your project. Enter the total wall area, number of coats, and the paint's coverage rate, and this calculator tells you the precise number of gallons to buy. It also lets you subtract standard doors and windows from the total area.

## Inputs

- **Total Wall Area** (ft²) — min 0 — Sum of all wall areas to be painted. Subtract windows and doors if desired.
- **Number of Coats** — min 1, max 5 — Most projects need 2 coats for even coverage
- **Coverage Rate** (ft²/gal) — min 1 — Standard interior paint covers about 350 ft² per gallon (~8.6 m² per liter)
- **Doors to Subtract** — min 0, max 20 — Standard door = ~21 ft². Enter 0 if already subtracted from wall area.
- **Windows to Subtract** — min 0, max 30 — Standard window = ~15 ft². Enter 0 if already subtracted from wall area.

## Outputs

- **Paintable Area** (ft²) — Total area after subtracting doors and windows
- **Total Coverage Needed** (ft²) — Paintable area multiplied by number of coats
- **Gallons Needed**
- **Gallons to Order** — Rounded up to nearest whole can
- **Liters Needed** (L)

## Details

The paint calculation formula:

Gallons = (Paintable Area × Number of Coats) / Coverage Rate

  - Paintable Area = Total wall area minus doors (≈21 ft² each) and windows (≈15 ft² each)

  - Number of Coats: Most paint jobs need 2 coats. Dark-to-light color changes may need 3+.

  - Coverage Rate: Standard interior latex paint covers about 350 ft²/gallon on smooth surfaces.

Coverage rate varies by paint type and surface texture:

  - Interior latex, smooth wall: 350-400 ft²/gal

  - Exterior latex: 250-350 ft²/gal

  - Textured surfaces: 200-300 ft²/gal

  - Primer: 200-300 ft²/gal

  - High-quality paint: 350-400 ft²/gal

Quick tip for calculating wall area: multiply the room perimeter by the ceiling height. For a 12×14 room with 8-foot ceilings: (12+14+12+14) × 8 = 416 ft².

## Frequently Asked Questions

**Q: How much area does a gallon of paint cover?**

A: A gallon of standard interior latex paint covers approximately 350-400 square feet on smooth surfaces with one coat. Coverage decreases on rough, textured, or porous surfaces.

**Q: How many coats of paint do I need?**

A: Two coats is standard for most applications. You may need three or more coats when making a dramatic color change (e.g., dark to light), painting over stains, or using low-quality paint. A primer coat can reduce the number of top coats needed.

**Q: Should I subtract doors and windows from the wall area?**

A: For accuracy, yes. A standard door is about 21 square feet and a standard window about 15 square feet. However, having a little extra paint is useful for touch-ups, so some painters skip this step intentionally.

**Q: How do I calculate wall area for a room?**

A: Measure the perimeter of the room (sum of all wall lengths) and multiply by the ceiling height. For example, a 10x12 room with 8-foot ceilings: (10+12+10+12) × 8 = 352 square feet of wall area.

**Q: Does primer count as a coat?**

A: Primer is a separate product with its own coverage rate (usually 200-300 ft²/gallon). It does not replace a top coat but reduces the number of top coats needed. Calculate primer separately from paint.

---

Source: https://vastcalc.com/calculators/construction/paint
Category: Construction
Last updated: 2026-04-21