Wall area → litres & cans of paint, with doors/windows deducted, coats and price — metric & US units, browser-only
- Runs locally
- Category Calculator
- Best for Getting a realistic range before a purchase, plan, workout, or schedule decision.
Most repaints over a similar colour need 2 coats. Dark-over-light or bare drywall often needs 3 (count primer separately).
What this tool does
A paint quantity calculator that turns a room into the number of cans you actually need to buy. Type the room length, width and height (or paste a wall area straight in), set how many coats you're doing, and the tool works out the net paintable area, the litres or gallons of paint required, and — the number people really want — how many whole cans to put in the cart, rounded UP because you can't buy three-fifths of a tin.
It subtracts doors and windows for you. Add a 1.9 m² door and a 1.4 m² window and the openings come straight off the wall area before the coat multiplier hits, so you don't pay to paint glass. You can list as many openings as the room has, each with its own size and quantity.
Coverage is the variable that makes or breaks the estimate. The default is 10 m² per litre (≈ 400 sqft per US gallon) — the conservative end of what Dulux, Nippon and Benjamin Moore print on their data sheets for smooth, primed interior walls. Bare drywall, textured render or a dark colour going over light all drink more paint, so the coverage field is editable and the result updates live.
Both unit systems are first-class: metric works in m² and litres with 5 L / 18 L / 1 L can presets, US imperial works in square feet and gallons with 1 gal / 5 gal presets. Add a price per can and you get an estimated material cost in your currency. Everything runs in your browser — no upload, no sign-up — and the inputs live in the URL so a "share this estimate" link reopens the same calculation for your painter or your partner.
Tool details
- Input
- Text + Numbers
- The page exposes text boxes, numeric controls, file pickers, or structured inputs depending on the tool.
- Output
- Live result + Copy
- The result area focuses on usable output, with copy, download, or preview actions when supported.
- Privacy
- Browser-side processing
- The main tool logic does not call an external API, so inputs normally stay in the current tab.
- Save / share
- Shareable URL state
- Key settings are encoded in the URL so another person can reopen the same setup.
- Performance budget
- Initial JS <= 10 KB
- No WASM budget is declared, keeping the tool quick to open on mobile.
- Best fit
- Calculator · Operations
- Category and role tags drive related tools, internal links, and quick fit checks.
How to use
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1. Input
Paste or drop your content into the tool panel.
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2. Process
Click the button. All processing is local in your browser.
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3. Copy / Download
Copy the result or download to disk in one click.
How Paint Calculator fits into your work
Use it for fast estimates, comparisons, and planning numbers before you make the final call.
Calculation jobs
- Getting a realistic range before a purchase, plan, workout, or schedule decision.
- Comparing scenarios by changing one input at a time.
- Turning rough assumptions into a number you can discuss.
Calculation checks
- Double-check units, dates, rates, and rounding assumptions.
- Treat health, finance, tax, and legal outputs as planning aids, not professional advice.
- Save the inputs that produced an important result so you can reproduce it later.
Good next steps
These links move the current task into a more complete workflow.
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- 3 Unit Converter Convert between length, weight, temperature, area, volume, speed, time — instant, browser-only Open
Real-world use cases
Quote a whole-apartment repaint before the hardware store
You're repainting a two-bedroom flat the weekend before move-in and want one shopping list, not three trips. Do each room in turn: 4 × 3.5 × 2.7 m bedroom, deduct one door and one window, two coats — that's about 33 m² net, 66 m² over two coats, 6.6 L, two 5 L cans. Repeat for the living room and hallway, jot the can counts, and you walk into the store knowing you need (say) five 5 L cans plus one 1 L can for touch-ups, instead of guessing and either running short mid-wall or carrying back an unopened tin.
Translate a US paint label for a metric job (or vice versa)
Your imported paint says "covers up to 400 sqft per gallon" but your walls are measured in square metres. Switch the tool to US units, type 400 in coverage, gallons in can size, and read the gallons you need; or flip to metric and let the default 10 m²/L stand in. The gallon↔litre and sqft↔m² conversions are baked in, so you stop doing the 3.785 and 10.764 arithmetic in your head at the paint counter.
Decide between a 5 L can and two 1 L cans for a small room
A box room needs 4.2 L. A single 5 L can covers it with 0.8 L to spare; five 1 L cans would cost more and leave the same leftover. By showing the leftover volume next to the can count, the tool turns "which pack size is cheapest" into a glance instead of mental math — especially handy when the 5 L tub is on offer and the 1 L tins aren't.
Check a contractor's paint quantity before you pay for it
A decorator says your stairwell "needs 12 litres." Measure the walls, deduct the openings, set the coats they quoted, and see whether 12 L is honest or padded. If the tool says 7 L for two coats and they quoted 12 L for two coats, either they're planning three coats, using a low-coverage paint, or rounding generously — now you can ask the right question instead of nodding along.
Plan a feature wall and trim separately
A single accent wall and the skirting are different paints and different areas. Use direct-area mode: type just the feature wall's square metres (height × width, no openings), two coats, read the litres — usually under one 1 L can. Then re-run with the trim's rough area. Two quick passes give you two precise tin sizes, so you don't over-buy a 5 L tub of accent colour you'll never finish.
Common pitfalls
Forgetting that primer is a separate coat. Two finish coats over fresh primer means three trips around the room with a roller, not two — set coats to 3 (or run primer as its own calculation) or you'll be one can short on the day.
Using the can's "up to" coverage as gospel. Data sheets quote the best case on a smooth sealed surface; bare drywall, texture, and dark-over-light can cut real coverage by 30-40%. If the wall is porous or you're making a big colour change, lower the coverage field rather than trusting the label.
Deducting tiny gaps but not the big ones, or vice versa. Skip the light switches and sockets (rounding noise), but always deduct full-size doors and windows — a couple of standard openings is several square metres, which is a noticeable fraction of one can on a small room.
Privacy
Every number stays in your browser. The room dimensions, coverage, coats and price are calculated locally in JavaScript — nothing is uploaded, logged, or sent to a server. Your unit system, can size and price preferences are saved in your browser's localStorage so the tool remembers them next visit; clearing site data wipes them. One thing to note: your room size, area and coats are encoded into the shareable URL (e.g. ?l=4&w=3.5&h=2.7&c=2) so a "share estimate" link reopens the same calculation. Those are harmless dimensions, but if you'd rather not put your floor plan in a link's query string, copy the result text instead of sharing the URL.
FAQ
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