Paint Coverage Calculator

Estimate gallons of paint needed for a room with deductions and coats

About this calculator

The Paint Coverage Calculator estimates how many gallons of paint a room needs. It computes wall area from room length, width, and ceiling height (feet), subtracts door and window deductions, multiplies by the number of coats, and divides by the paint's coverage rate (default 350 sq ft per gallon). Results include the exact decimal gallons and the whole gallons to buy. Missing deductions default to zero; non-positive dimensions return an error.

How to use the Paint Coverage Calculator calculator

  1. Enter your values into the input fields.
  2. Read the result — it updates instantly as you type.
  3. Adjust the inputs to compare scenarios.
  4. Copy the page URL to share the exact calculation.

Common examples

  • 12×10 ft room, 8 ft ceilings, 40 sq ft openings, 2 coats → 624 sq ft to cover → buy 2 gallons
  • 15×12 ft room, 9 ft ceilings, 60 sq ft deductions, 1 coat → 426 sq ft → 1.22 gal, buy 2
  • 20×18 ft room, 10 ft ceilings, 100 sq ft openings, 2 coats at 400 sq ft/gal → 3.30 gal, buy 4

Frequently asked questions

How does the Paint Coverage Calculator calculator work?

Enter your numbers and the calculator applies the standard formula for this everyday task, showing the result and how it was reached. It handles the unit and rounding details so you do not have to.

When would I use the Paint Coverage Calculator calculator?

Whenever this comes up in daily life — planning, shopping, home projects, travel or work — and you want a quick, dependable answer instead of estimating or working it out by hand.

How accurate are the results?

The math runs at full precision internally and only the displayed value is rounded for readability. For real-world use the practical limit is the accuracy of the numbers you enter, not the calculation.

Can I share a specific calculation with someone else?

Yes. Every value you enter updates the URL, so copying the address bar and sharing the link reopens the exact same calculation for whoever clicks it.