Paint Calculator
Work out how many gallons of paint you need for any room. Enter room dimensions, doors and windows, paint type, and number of coats.
Free Home Improvement Calculators
Work out exactly how much material your project needs before you drive to the store. Three free home improvement calculators, accurate industry coverage rates, results in seconds — no signup, no downloads.
Choose a calculator
Concrete Calculator
Calculate bags or cubic yards of concrete for slabs, footings, walls, and columns. Picks the right bag sizes and adds a waste allowance.
Flooring Calculator
Find how many boxes of hardwood, laminate, vinyl plank, or tile to buy, with waste and underlayment included.
Material Math Challenge
Test your knowledge of paint, concrete, and flooring calculations. Five quick questions with timed answers — see how many you can get right.
How much material do you need?
Every material is estimated differently, and the costly mistake is usually the same in each case: ordering the exact calculated amount and running short halfway through. Here is the short version for each.
How much paint do I need?
Add up the wall area, subtract the openings, then divide by the coverage rate. A standard interior door takes about 21 sq ft out of the wall and a standard window about 15 sq ft. One gallon of interior latex covers roughly 350 sq ft per coat on smooth, primed drywall — closer to 250 sq ft on rough or porous surfaces. Most rooms need two coats, and you should add about 10% on top for cutting in, roller waste, and future touch-ups. Our paint calculator does the whole thing, including ceilings.
How much concrete do I need?
Concrete is ordered by volume, so the depth matters as much as the footprint. Once you pass roughly 20 bags' worth, ready-mix delivered by the cubic yard is usually cheaper than hauling bags. One cubic yard covers about 81 sq ft at 4 inches thick. Always add a 5–10% waste allowance: subgrade is never perfectly level, some material spills, and finishing loses a little. Running short mid-pour is far more expensive than over-ordering. Try the concrete calculator for slabs, footings, walls, and columns.
How much flooring do I need?
Flooring is sold by the box, not by the square foot, so the answer is always a whole number of boxes. Start from the room area, then add a waste factor: 5–10% for a straight lay in a rectangular room, about 15% for diagonal or herringbone patterns, and up to 20% if the room has a lot of angles or alcoves. Remember underlayment, which is sold separately and sized to the floor area. The flooring calculator handles all of it, including multiple rooms.
Coverage and waste rates at a glance
These are the industry-standard figures our calculators use. Real results shift with surface texture, porosity, and how carefully the material is applied.
| Material | What to measure | Standard coverage | Typical waste | Sold by |
|---|---|---|---|---|
| Interior paint | Wall area, minus doors and windows | 350 sq ft per gallon per coat | 10% | Gallon or quart |
| Primer | Same as paint, one coat | 300 sq ft per gallon | 10% | Gallon |
| Exterior paint | Wall area, minus openings | 350 sq ft smooth / 250 sq ft rough | 10–15% | Gallon |
| Concrete | Volume: length × width × depth | 1 cubic yard = 81 sq ft at 4 in | 5–10% | Cubic yard or bag |
| Flooring | Floor area, plus waste | 11–23 sq ft per box by product | 10–15% | Box or carton |
Why use these calculators
Ordering too much material wastes money you cannot get back. Ordering too little means a second trip to the store, and for paint it can mean a batch that does not quite match. Our calculators use published industry coverage rates rather than optimistic marketing numbers, so you get a realistic figure the first time.
Each tool runs entirely in your browser. Your room dimensions are never uploaded to a server, never stored, and never used for anything — you could disconnect from the internet after the page loads and the calculator would still work.
EasyCalc is independent. It is not funded by, affiliated with, or owned by any paint, concrete, or flooring manufacturer or retailer. A calculator paid for by a supplier has a quiet incentive to round up, and we would rather not have that problem. You can read more on our about page, or get in touch if a result looks wrong.
Frequently asked questions
Are the calculators really free?
Yes. Every calculator on EasyCalc is free, with no account, no email address, no paywall, and no usage limit. Use them as often as you like.
Do I need to install anything?
No. The calculators run in a normal web browser on desktop, tablet, or phone. There is no app to download and nothing to sign up for.
Are my measurements uploaded or stored anywhere?
No. All the maths happens in your own browser. Your room dimensions are never sent to our server, never saved, and never shared. Share links work by putting the numbers into the link itself, so nothing is stored on our side.
How accurate are the estimates?
They are based on standard industry coverage rates — for example 350 sq ft per gallon for interior latex on smooth, primed drywall. Real-world results shift with surface texture, porosity, colour changes, and how the material is applied, so treat the result as a planning figure rather than a contractor's quote. Each calculator lets you enter a custom coverage rate if you know what your specific product achieves.
Can I share my results with someone else?
Yes. Every calculator has a share button that copies a link containing your numbers. Send it to a contractor, a partner, or whoever is picking up the materials and they will see exactly the same result.
Do the calculators support metric units?
Yes. Every calculator works in both imperial and metric. Use the Imperial / Metric toggle at the top of the input panel to switch between feet/inches/gallons/cubic yards and metres/centimetres/litres/kilograms. Your selection is remembered on your device, and shareable links include the unit you used.
What if my room is not a simple rectangle?
Break it into rectangles and add the areas together, or use the custom-area field where the tool offers one — the flooring calculator accepts a total area directly, and the paint calculator lets you enter a custom coverage rate for awkward surfaces. For anything genuinely irregular, over-measuring slightly is cheaper than running short.