How to Calculate How Much Paint You Need
Planning a painting project starts with one essential question: how much paint do I actually need? Buying too little means extra trips to the store mid-project, while buying too much wastes money. Our free paint calculator takes the guesswork out by giving you an accurate estimate based on your room's exact dimensions.
The basic formula is straightforward: measure your wall area (length × height for each wall), subtract openings like doors and windows, then divide by the paint's coverage rate. Most interior paints cover approximately 350–400 square feet per gallon on smooth surfaces. Textured walls, bare drywall, or dark-to-light color changes may require additional coats, reducing effective coverage to around 200 square feet per gallon.
A few pro tips to keep in mind: always round up to the nearest full gallon, since partial cans are not sold at most retailers. If you are applying two coats (recommended for most projects), the calculator already accounts for that. Also consider keeping a small amount of leftover paint for future touch-ups—store it in a cool, dry place and it will last for years.
Once you have your paint quantities figured out, you can use RoomLab's AI room visualizer to preview different wall colors in your actual space before committing. Upload a photo of your room and experiment with colors, finishes, and accent walls to find the perfect look.