Paint Calculator
Enter your room dimensions and the calculator will tell you how many gallons of paint you need — accounting for doors, windows, and multiple coats.
Room dimensions
350 ft²/gal is typical
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Gallons needed
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ft² to paint
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1-gallon cans
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5-gallon buckets
Tip: buy a 5-gallon bucket when you need 4+ gallons — it's almost always cheaper per gallon.
How to Calculate Paint
Wall area equals the perimeter of the room multiplied by the ceiling height, minus the area of doors and windows. Multiply by the number of coats, then divide by the coverage rate of your paint.
Paint Coverage Rates
| Paint type | Typical coverage |
|---|---|
| Standard flat / eggshell | 350–400 ft²/gal |
| Premium paint + primer | 300–350 ft²/gal |
| Ceiling paint | 300–350 ft²/gal |
| Exterior latex | 300–400 ft²/gal |
| Primer (porous surface) | 200–300 ft²/gal |
How Many Coats of Paint Do I Need?
- 1 coat — touching up or using same colour with high-quality paint-and-primer
- 2 coats — standard for most repaints and colour changes; recommended for best results
- 3 coats — covering a dark colour with a light one, painting bare drywall without primer, or using low-quality paint
Surface Prep and Primer
Proper surface prep dramatically affects how much paint you use and how long it lasts:
- Fill holes and cracks with spackling compound; sand smooth when dry
- Clean walls to remove grease, dust, and mildew before painting
- Prime bare drywall — unprimed drywall soaks up paint; apply one coat of drywall primer before topcoating
- Prime stained areas with a stain-blocking primer (shellac or oil-based) before latex topcoat
- Sand glossy surfaces to give the new paint something to grip
Paint Finish Guide
| Finish | Best for | Notes |
|---|---|---|
| Flat / matte | Ceilings, low-traffic walls | Hides imperfections; hard to clean |
| Eggshell | Living rooms, bedrooms | Slight sheen; easier to clean |
| Satin | Hallways, kids' rooms | Durable; good moisture resistance |
| Semi-gloss | Kitchens, bathrooms, trim | Cleans easily; shows wall flaws |
| Gloss / high-gloss | Doors, cabinets, furniture | Very durable; very unforgiving |
Frequently Asked Questions
Do I need to buy separate paint for the ceiling? Yes, dedicated ceiling paint is recommended. Ceiling paint is typically flat finish and formulated to minimise splatter and show even coverage overhead. It is also often white or off-white. Use our calculator with "Include ceiling" checked to estimate the ceiling separately.
How do I calculate paint for trim and doors? This calculator focuses on wall and ceiling area. For trim (baseboards, door frames, window casing), measure the linear footage and multiply by the trim height (typically 3–5 inches for baseboards, 3 inches for door casing). One quart of trim paint covers approximately 100 linear feet of standard-sized trim.
Can I use the same paint for walls and trim? Technically yes, but trim paint is typically semi-gloss or gloss for durability, while walls use eggshell or satin. Using wall paint on trim will not last as long. If you're doing a full room renovation, the flooring calculator can help you estimate new floor materials at the same time.
