Paint Calculator

Calculate exactly how many gallons of paint you need for walls, ceilings, and trim. Enter room dimensions, ceiling height, number of coats, and subtract doors and windows for an accurate estimate.

Room Paint Calculator

Paint Calculation Formula

Wall Area = 2 × (length + width) × height Subtract = doors × 20 sq ft + windows × 15 sq ft Net Area = Wall Area − Subtractions Gallons = (Net Area / coverage) × coats Ceiling Area = length × width (if including ceiling)

Paint Coverage by Finish

FinishCoverage per GallonBest For
Flat / Matte400–450 sq ftCeilings, low-traffic walls
Eggshell350–400 sq ftLiving rooms, bedrooms
Satin350–400 sq ftKitchens, bathrooms, trim
Semi-Gloss300–350 sq ftTrim, cabinets, doors
Gloss250–300 sq ftAccent features, furniture

Frequently Asked Questions

How many coats of paint do I need?+
Most paint projects require 2 coats for full, even coverage. Going from a dark color to a light one (or vice versa) may need 3 coats. Using a primer first reduces the number of top-coat applications needed.
Should I use primer?+
Yes, primer is recommended when painting over dark colors, new drywall, stained surfaces, or switching color families dramatically. Primer seals the surface and improves paint adhesion and color accuracy.

About the Paint Calculator

This free paint calculator helps you get accurate results instantly without needing to work through the math manually. Whether you need a quick estimate or a precise figure, having a reliable tool on hand saves time and reduces errors compared to manual calculation.

How to Use This Calculator

  1. Enter your values in the input fields above. Each field is labeled to guide you.
  2. Double-check your inputs — results are only as accurate as the numbers you enter.
  3. Click the Calculate button to see your result instantly.
  4. Use the result for your planning, budgeting, or decision-making.

Why Accurate Calculations Matter

Small errors in math calculations can compound into significant problems. A 1% miscalculation in a budget or measurement can translate to hundreds or thousands of dollars in wasted resources, or result in having to redo work entirely. This calculator uses the standard formulas and methods to give you reliable results you can trust.

Tips for Getting the Best Results

Frequently Asked Questions

Is this calculator free? Yes — completely free with no account, login, or payment required. Use it as many times as you need.

How accurate are the results? This calculator uses the standard formulas for paint calculations. Results are accurate for typical use cases. For specialized or high-stakes applications, consult a professional.

Does it work on mobile? Yes. This calculator is fully responsive and works on smartphones, tablets, and desktops.