Paint Calculator
Litres of paint needed.
Litres of paint needed.
How to use Paint Calculator
- Enter total wall area, or a wall's length and height
- Set the number of coats and your paint's coverage per litre
- Add each door or window to subtract about 1.8 square metres
- Read how many litres of paint to buy
About Paint Calculator
The Paint Calculator works out how much paint your project needs before you head to the shop. Enter the total wall area, or type a wall's length and height and it works out the area for you, then set how many coats you're applying and the coverage figure from your paint tin. It automatically subtracts about 1.8 m² for every door and window you list, so you only account for the surface you'll actually cover, and it rounds the answer up to whole litres so you never run short mid-coat.
Coverage is the number that matters most: most wall paints spread across roughly 6–12 m² per litre, and the tool defaults to 10 but lets you match your own tin exactly. Because you set that figure yourself, it works for any brand or retailer — whether you picked up Sherwin-Williams, a Lowe's own-label, or supermarket emulsion — instead of guessing from a store's own estimator. It's built in metres and litres, so if your measurements are in square feet, convert them first (1 m² ≈ 10.76 sq ft). Once you know the litres, multiply by your paint's price per tin to turn the estimate into an interior or exterior job cost.
It's completely free with no sign-up. Everything runs entirely in your browser — nothing you type is uploaded or stored on a server, so your measurements stay private on your own device.
Frequently asked questions
- How does the paint calculator work out how much paint I need?
- It uses paintable area × number of coats ÷ coverage per litre. Paintable area is your total wall area minus roughly 1.8 m² for each door or window you enter. The result is rounded up to whole litres so you know how much to buy.
- What coverage per litre should I use?
- Most emulsion and wall paints cover about 6–12 m² per litre depending on the paint, surface, and colour. The default is 10 m²/L, but check your tin's label and enter that figure for the most accurate estimate. Porous or textured surfaces use more paint.
- Is this the Sherwin-Williams paint calculator?
- No, it's a free independent tool and isn't affiliated with Sherwin-Williams, but it does the same job for any Sherwin-Williams paint. Read the coverage figure off the tin or product page, enter it with your wall area and coats, and you'll get the quantity to buy.
- Can I use it instead of the Lowe's paint calculator?
- Yes. This calculator isn't tied to any retailer, so it works whether you're buying from Lowe's, a hardware store, or online. Just enter the coverage rate for the specific paint you've chosen along with your room measurements.
- Can I use this paint calculator in square feet?
- The calculator is built in metres and litres. If your wall measurements are in square feet, convert them to square metres first by dividing by 10.76 — for example, 400 sq ft ÷ 10.76 ≈ 37 m² — then enter that figure as your total wall area.
- How do I work out the cost of painting a room?
- First use the calculator to get the number of litres you need, then multiply that by the price per litre or per tin of your chosen paint. Adding primer, rollers, and tape gives you a fuller budget for an interior or exterior job.
- Can I use it for exterior house painting?
- Yes. Measure the outside walls the same way — total area, or length × height — and subtract the doors and windows. Exterior masonry and render are often more porous, so use a lower coverage figure (closer to 6 m²/L) and the estimate scales up automatically.
- How many coats of paint should I add?
- Two coats is standard for most repaints and gives even colour. Use three when painting a light colour over a dark wall, covering stains, or working with a thin paint. Enter that number and the calculator multiplies the paintable area accordingly.
- Why does it round the litres up?
- Paint is sold in fixed tin sizes, and running out mid-coat leaves visible joins. The main result rounds up to the nearest whole litre so you buy enough to finish the job, while the stat grid also shows the exact litres needed for reference.
- Can I calculate paint for a whole room?
- Yes. Add up the area of all the walls you want to paint and enter it as the total wall area, or measure the combined length and use your ceiling height. Then enter the total number of doors and windows across those walls to subtract them.
- Is this paint calculator free to use?
- Yes, it's completely free with no account, sign-up, or limits. Use it as many times as you like.
- Is my data uploaded or stored anywhere?
- No. The calculator runs entirely in your browser using JavaScript. Your measurements are never sent to a server, saved, or shared — everything stays on your device.