What is a typical paint spread rate?

Most interior paints cover 350–400 sq ft per gallon (32–37 m² per liter) on smooth surfaces. Rough or porous surfaces reduce coverage to around 200–300 sq ft per gallon. Check your paint can label for the manufacturer's stated spread rate.

How many coats of paint do I need?

Two coats are standard for most interior painting jobs. Priming bare drywall or making a dramatic color change (dark to light or vice versa) may require three coats. One coat is only sufficient for touch-ups or very minor refreshes.

What waste factor should I use?

A 10 % waste factor is reasonable for professional painters on smooth surfaces. Use 15 % for DIY projects or lightly textured walls, and 20 % for heavy texture, spray application, or when painting around many obstacles such as windows and doors.

Should I include windows and doors in the square footage?

For quick estimates it is fine to ignore them. For accuracy, subtract roughly 20 sq ft (1.9 m²) per standard door and 15 sq ft (1.4 m²) per standard window from the total wall area before calculating.

Can I use this for ceilings?

Yes. Add a surface row for the ceiling, enter its width and length, and choose a spread rate appropriate for ceiling paint (typically similar to wall paint). Ceilings often need only one coat if the color is unchanged.

How do I convert gallons to liters?

One US gallon equals approximately 3.785 liters. The calculator shows both units automatically once you click Calculate.

Paint Coverage Calculator

Name: Paint Coverage Calculator
Availability: InStock
Author: Nham Vu

Enter your room dimensions and paint spread rate to find out exactly how many gallons or liters of paint you need, including a waste allowance.

Unit System

Surfaces

Number of Coats

Waste Factor (%)

Paint Spread Rate (sq ft per gallon)

Typical interior paint: 350–400 sq ft/gal (32–37 m²/L)

Enter your room details and click Calculate

Summary

Enter your room dimensions and paint spread rate to find out exactly how many gallons or liters of paint you need, including a waste allowance.

How it works

Enter the dimensions of each surface (width and height) or the total square footage.
Set the number of coats you plan to apply.
Enter the spread rate from your paint can label (e.g. 350 sq ft per gallon).
Add a waste factor percentage (typically 10–15 %) to account for touch-ups and uneven application.
Click Calculate to see the total paint volume in gallons and liters.

Use cases

Estimate paint for a bedroom, living room, or entire house.
Plan a commercial painting project with multiple coats.
Compare how many cans to buy at the hardware store.
Avoid over-purchasing by accounting for exact spread rates.
Account for extra paint needed for textured or porous surfaces.
Switch between US gallons and liters for international paint brands.

Frequently Asked Questions

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Last updated: 2026-05-23 · Reviewed by Nham Vu