Paint
Calculator
Enter your room dimensions and find out exactly how much paint you need — in gallons or liters, with cost estimates.
Enter your room dimensions above to get your paint estimate.
How the paint calculator works
The calculator computes total paintable wall area by multiplying the room perimeter (2 × length + 2 × width) by wall height, then subtracting standard door openings (~21 sq ft / 2 m² each) and windows (~15 sq ft / 1.4 m² each). It multiplies by your chosen number of coats and divides by 400 sq ft per gallon — the industry-standard coverage rate for smooth, primed interior walls. The cost estimate uses a range of $30–$50 per gallon to cover budget through premium paint options.
Frequently asked questions
Frequently Asked Questions
Q1 How much paint do I need for a room?
It depends on the room size. Measure the length and width of your room and the wall height (standard is 8 feet / 2.4 meters). Multiply the perimeter by the height to get gross wall area, subtract doors (~21 sq ft each) and windows (~15 sq ft each), then divide by 400 sq ft (one gallon's coverage). Multiply by number of coats. Our calculator does this math instantly.
Q2 How much area does one gallon of paint cover?
One gallon of interior paint typically covers about 350–400 square feet on smooth, primed walls. Textured, porous, or unpainted surfaces absorb more paint and may only get 250–300 sq ft per gallon. Always buy 10% extra for touch-ups.
Q3 How many coats of paint do I need?
Most rooms need 2 coats for even coverage and true color. You may need 3 coats if you're painting a dark color over a light one, or covering bold existing colors. A primer coat is recommended when making dramatic color changes or painting new drywall.
Q4 How much does paint cost?
Interior paint ranges from $25–$50+ per gallon depending on quality. Budget paints start around $25, mid-range options are $30–40, and premium paints (Benjamin Moore, Sherwin-Williams) run $40–60+. Higher-quality paint typically provides better coverage and durability, often requiring fewer coats.
Q5 Should I subtract ceiling area from my calculation?
This calculator measures wall area only, not ceiling. If you plan to paint the ceiling too, calculate that separately: multiply room length × width for ceiling area, then divide by 400 to get additional gallons needed.
Q6 Can I visualize paint colors before buying?
Yes — download the Intero app to upload a photo of your room and see AI apply different paint colors and design styles directly to your walls. It's the fastest way to preview colors before committing.
Visualize the color before you paint
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