Complete Guide: How Many Gallons of Interior Paint Do You Need?
An interior paint calculator converts your room's dimensions into the exact wall surface area, subtracts doors and windows, and divides by your paint's coverage rate to tell you how many gallons to buy. This free tool works in both imperial (feet/gallons) and metric (meters/liters) units.
💡 Quick Summary
Wall area = room perimeter × height, minus standard door and window openings. Multiply by your number of coats, then divide by your paint's coverage rate (typically 350 sq ft per gallon) to get total gallons.
How Many Coats Do You Really Need?
- 2 coats: Standard for most interior painting jobs, especially when changing colors.
- 1 coat: Sometimes sufficient for touch-ups or when painting the same color over a similar existing shade with good coverage paint.
- 3 coats: Often needed for dramatic color changes, such as painting over a dark color with white or a pastel shade.
Step-by-Step Instructions
- Enter your room's length, width, and height.
- Enter the number of doors and windows in the room.
- Select the number of coats you plan to apply and your paint's coverage rate.
- Click Calculate.
- Review your total paintable area and gallons needed, then use 📋 Copy Summary to save your results.
Tip: Coverage rates vary by paint brand, sheen, and wall texture. Always check the coverage figure printed on your specific paint can for the most accurate estimate.