Quick Room Paint Estimator
Instantly estimate paint cans needed for any room.
Enter dimensions and ceiling height to get wall area, gallons needed, and number of cans to buy.
Paint Needed
Wall Area = (2 × (Length + Width) × Height) - Openings
Paint Needed = (Wall Area × Number of Coats) / Coverage Rate
This calculator estimates how much paint you need for all four walls of a rectangular room. It automatically subtracts approximately 50 sq ft (5 m2) for standard doors and windows.
What the variables mean:
- Room Length and Width – the floor dimensions of your room
- Ceiling Height – floor-to-ceiling distance
- Coats – how many layers of paint you will apply (default is 2)
- Coverage rate – 350 sq ft (32 m2) per gallon, or 10 m2 per liter
Coverage reference:
| Paint Amount | Covers (1 coat) |
|---|---|
| 1 gallon (3.8 L) | ~350 sq ft (32 m2) |
| 1 liter | ~10 m2 (108 sq ft) |
| 5 gallons (19 L) | ~1,750 sq ft (160 m2) |
Practical examples:
- A 12 ft × 10 ft room with 8 ft ceilings: wall area = 302 sq ft (after subtracting openings). Two coats need about 1.7 gallons.
- A 4 m × 3 m room with 2.5 m ceilings: wall area = 30 m2 (after subtracting openings). Two coats need about 6 liters.
When to use this calculator: Use it before any painting project to buy the right amount of paint. Over-buying wastes money, while under-buying means an extra trip to the store and potential color-matching issues between batches.
Tips:
- Textured walls absorb more paint – add 15-20% to your estimate.
- Dark-to-light color changes may require a primer coat plus two top coats.
- Most professionals recommend two coats for an even, durable finish.
- The calculator supports both feet and meters – select your preferred unit before entering dimensions.
- Results always show both gallons and liters for convenience.