Wall Painting Calculator
Estimate paint gallons, cans to buy, and total cost for any room. Subtract doors and windows, add the ceiling, set how many coats, and account for waste — all in one place.
Room & paint setup
Room dimensions
Openings to subtract
Container & cost
Wall preview & breakdown
Walls drawn unrolled to scale. 52 ft perimeter × 8 ft tall.
Buying guide
- Buy in larger cans: A single 5-gallon bucket is usually cheaper per gal than several small ones.
- Save the leftovers: Keep a small amount for touch-ups — colour batches can vary later.
- Primer first: New drywall or strong colour change adds an extra coat — set coats to 3.
- Don't forget trim: Baseboards, doors, and frames usually need a different finish (semi-gloss) — calculate them separately.
Good to know
This calculator gives a practical estimate for a typical rectangular room. Textured walls, deep colour changes, and sloped or vaulted ceilings can push real paint usage higher.
About the Wall Painting Calculator
The Wall Painting Calculator helps you work out exactly how much paint you need before you head to the hardware store. It takes your room dimensions, subtracts doors and windows, and applies the paint coverage rate so you don't end up with half-empty cans — or worse, run out mid-job.
It supports both imperial (feet and gallons) and metric (metres and litres) units. You can choose how many coats to apply, factor in a waste percentage for spills and roller losses, and instantly see how many cans to buy plus the total cost.
How to Use the Wall Painting Calculator
- Pick your unit. Toggle between feet or metres.
- Enter the room size. Length, width, and wall height of the room.
- Decide on the ceiling. Tick the box to include it.
- Subtract openings. Add how many doors and windows there are, with their average size.
- Pick a paint type. Tap a preset chip (flat, eggshell, semi-gloss, primer, textured) or enter your own coverage rate from the can label.
- Choose coats and waste. Two coats is standard; 10% waste is a safe default.
- Set the can size and price. The calculator rounds up to whole cans and shows your total cost.
Common Use Cases
Single bedroom refresh
Repainting one bedroom in a new colour — 2 coats, eggshell finish, 1 gallon cans.
Whole-room renovation
New drywall — primer + 2 colour coats (set coats to 3), 5-gallon buckets are cheaper.
Living room with feature wall
Calculate the main paint amount, then run the tool again with a smaller perimeter for the accent colour.
Rental turnover
Flat / matte finish across walls and ceiling in a neutral colour — quick to apply and easy to touch up.
Frequently Asked Questions
How much paint do I need for a 12×14 room?
A 12 ft × 14 ft room with 8 ft walls, one door, and two windows works out to about 380 ft² of paintable wall. With two coats and 10% waste, that's roughly 2.2 gallons — round up to three 1-gallon cans, or buy one 5-gallon bucket if you're also doing the ceiling.
How many coats of paint do walls usually need?
Two coats is the standard for most repaints. Use three when going from a dark colour to a light one, or when painting fresh drywall (one is essentially primer).
What's a typical paint coverage rate?
Smooth interior walls usually get 350–400 ft² (9.5–11 m²) per gallon for one coat. Textured walls absorb more — drop to around 250 ft² (7 m²) per gallon. Always check the actual can; the calculator's chips are typical averages.
Should I include the ceiling in the same total?
Only if you're using the same paint. Ceilings are usually painted with a flat ceiling-specific paint, so it's often cleaner to run the calculator twice — once with the ceiling box ticked using ceiling paint, and again for walls.
Why does the calculator add a waste percentage?
Real-world painting loses paint to drips, roller absorption, and brush cleanup. Ten percent is a safe default for DIY jobs; lower it to 5% if you're confident, or raise it to 15% for older, thirstier walls.
Does this work for litres and metres?
Yes — toggle the unit switch at the top. Coverage rates change to m² per litre, can sizes switch to 1 L, 2.5 L, 5 L, 10 L presets, and all results recompute automatically.