These free home improvement calculators handle the measuring and math for the jobs you are actually doing this weekend, from painting a bedroom to wiring a shed. Work out gallons, boxes, cubic yards and bags before you load the car. Every calculation stays on your own phone or computer, no account needed.
Work out gallons with the Paint Calculator, boxes with the Tile Calculator and Flooring Calculator, cubic yards with the Concrete Volume Calculator, and bags with the Mulch and Soil Calculator before you load the car. The Wallpaper Roll Calculator and Grass Seed Calculator cover the same ground for rooms and lawns. Type your room dimensions, get the answer, and buy once instead of making a second trip to the store.
The measuring is easy to get wrong once spacing is involved. Check gaps with the Fence Post Spacing Calculator, get sensible steps from the Stair Rise and Run Calculator, size lumber with the Board Feet Calculator, and look up the right bit in the Pilot Hole and Drill Bit Chart. If your tape and your instructions disagree, the Fractional Inches to mm Converter sorts that out before you cut anything.
Every calculation runs on your own phone or computer. Your room dimensions, pool size and material costs are never sent anywhere, so nothing is stored or logged, and you will never hit an email gate or a contractor quote form before seeing your number. Hobby and electronics jobs work the same way, from the LED Resistor Calculator and Battery Life Estimator to the Knitting Gauge Calculator, and once a page has loaded it keeps working even if the signal drops out in the garage.
Multiply each wall's width by its height, add the walls together, then divide by the coverage printed on the can, usually 350 to 400 square feet per gallon per coat. A 12 by 12 foot room with 8 foot ceilings is roughly 384 square feet of wall, so about one gallon per coat, or two gallons for two coats. Subtract large windows and doors, and the Paint Calculator handles the arithmetic and the openings for you.
Add 10 percent to the measured area for a straightforward straight-lay installation, and 15 to 20 percent for diagonal or herringbone patterns, small mosaic tiles, or rooms with many cuts around cabinets and alcoves. Offcuts and breakage are unavoidable, and buying a spare box from the same batch protects you against dye lot differences during a later repair. The Tile Calculator and Flooring Calculator let you set your own waste percentage.
No. Every calculator on this page runs entirely in your browser, so the numbers you type never leave your device and are never uploaded, stored or logged on a server. There is no account to create, no email address to hand over and no cookies tracking what you calculated. Because nothing depends on a round trip to a server, results appear instantly, and a page that has already loaded still works without a connection.