Updated 2026-04-30 · Methodology: named formula library

Paint Calculator

Calculate how many gallons of paint you need for a room based on wall dimensions and coats.

Room Length (ft)

Room Width (ft)

Ceiling Height (ft)

Number of Coats

Paint Needed

3 gallons

You need approximately 3 gallons of paint for a 12' × 10' room with 8' ceilings (2 coats).

Wall Area352 sq ft

Gallons Needed2.0

Coverage350 sq ft/gal

Coats2

Data sources: CalcIntel Formula Library

Why This Calculation Matters

The Paint Calculator helps you price and order materials correctly the first time. Short-ordering means extra trips, delays, and rushed decisions; over-ordering means wasted money and disposal hassle. A precise takeoff, plus a standard 10% waste factor, is the sweet spot.

How to Use This Calculator

Enter your values in the input fields, each one has a label and help text explaining what to type.
Results appear instantly as you type; there's no "calculate" button to press.
Change any input to compare scenarios side by side.

All math happens in your browser. Nothing you type is sent to a server, saved, or shared.

Ordering & Waste Factor

Always add roughly 10% to the calculated quantity. Cuts, edge losses, breakage, and mistakes happen on every project. A small surplus is far cheaper than a supply run mid-pour or mid-install.

Paint Coverage

One gallon of paint covers approximately 350-400 square feet (one coat). Calculate total wall area, subtract doors and windows, then divide by coverage and multiply by number of coats.

Typical Coverage Rates

Flat/matte: 350-400 sq ft/gallon
Eggshell/satin: 350-400 sq ft/gallon
Semi-gloss: 350-400 sq ft/gallon
Primer: 200-300 sq ft/gallon (porous surfaces need more)

Formula

Coverage = wall area ÷ sq ft per gallon (typically 350). Double for two coats. Subtract windows and doors (~21 sq ft per door, ~15 sq ft per window) for accuracy.

Worked Example

12 ft × 10 ft room, 9 ft ceiling

length: 12
width: 10
height: 9
Result: 1 gallon (incl. 1 coat)

Wall area ~396 sq ft. 1 gallon covers 350 sq ft; round up.

When to Use This Calculator

Estimate material quantities before ordering, avoid short-loads and wasteful overbuy.
Price a bid or budget for a customer accurately.
Spot errors in a supplier's take-off or quote.

Limitations & Common Mistakes

Add ~10% to material totals for waste, cuts, and breakage.
Local building codes, load requirements, and soil conditions may change what you need, always confirm with your permit office or structural engineer.
Prices vary by region and supplier; request current quotes before ordering.

Frequently Asked Questions

How does the Paint Calculator work?

Enter your room length (ft) (default: 12) and any other inputs; the calculator instantly applies its paint formula and shows the result with details. All math runs in your browser; nothing is sent to a server.

Is the Paint Calculator accurate for materials decisions?

It uses standard, documented formulas that match published references. For high-stakes materials decisions, verify the result against an authoritative source (industry calculator, professional advisor, or government data). The calculator is a planning estimate, not a substitute for professional judgment.

What inputs does the Paint Calculator require?

4 inputs: Room Length (ft), Room Width (ft), Ceiling Height (ft), Number of Coats. Each has a sensible default; replace with your own values to get a result tailored to your situation.

Can I bookmark or share the Paint Calculator?

Yes — the URL is stable: https://www.calcintel.com/calculator/paint. Inputs reset to defaults on each visit (no input is stored), so screenshot or copy the result if you want to preserve a specific scenario.