Free paint calculator with instant results.
Estimate how many gallons of paint you need, total coverage, and project cost for rooms and walls. Ideal for homeowners, DIY projects, and contractors.
Use this paint calculator to accurately estimate how many gallons of paint you need for walls, rooms, and full interior or exterior projects. It calculates total surface area based on your dimensions, then factors in coats, coverage rate, and optional cost per gallon. This ensures you avoid underbuying or overspending on paint. Whether you're a contractor or DIY homeowner, it delivers fast, reliable estimates for smarter project planning.
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Enter room dimensions (length, width, height) to calculate total wall surface area. Select number of coats and paint coverage per gallon to estimate total gallons needed and project cost instantly.
To calculate how much paint you need, multiply the perimeter of the room by wall height to get total wall area. Then multiply by the number of coats and divide by the paint’s coverage rate per gallon. This calculator does all of that instantly.
Paint is typically sold by the gallon, and most products cover around 300–400 square feet per gallon. This calculator estimates the number of gallons required based on your exact room dimensions and number of coats.
For a 12 ft × 15 ft room with 8 ft walls and 2 coats:
A typical room may cost $100–$300 in paint for DIY projects, while professional painting can cost significantly more depending on labor and prep work.
Accurate paint estimation helps prevent overspending and ensures you don’t run out mid-project. Professional painters calculate surface area, number of coats, and coverage rates to determine exact material needs. This calculator follows the same approach for reliable estimates.
How do I calculate how much paint I need?
Measure total wall surface area (length × height for each wall), add all walls together, multiply by number of coats, then divide by paint coverage per gallon.
Do I need to include windows and doors in the calculation?
For more accurate results, subtract large windows and doors from the total wall area since they reduce the amount of paint needed.
How many gallons of paint do I need for a room?
Most standard rooms require 1–3 gallons depending on room size, number of coats, and surface texture. Larger or rough surfaces will require more paint.