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Kalku

Free construction calculators

Ten of the calculators from the Kalku app, running in your browser with the same formulas. Feet, inches and fractions or metric, nothing to install, and a link that keeps your numbers.

Concrete CalculatorCubic yards, bags and the order with waste for a slab, a footing or round columns.Stair CalculatorRisers, treads, stringer length and stairwell opening from the floor-to-floor rise.Roof Pitch CalculatorPitch, angle and grade from rise and run, and the rafter lengths that go with them.Feet and Inches CalculatorAdd, subtract, multiply and divide feet, inches and fractions down to 1/64".Gravel CalculatorCubic yards and tons of gravel, crushed stone or sand for a driveway or a base.Mulch CalculatorCubic yards or bags of mulch, topsoil or compost to cover a bed to a depth.Drywall CalculatorSheets, joint compound, tape and screws for a room, ceiling included.Paint CalculatorGallons or litres of paint for a room, with coats, doors and windows allowed for.Tile CalculatorTiles and boxes for a floor or a wall, grout joints and waste counted.Board Foot CalculatorBoard feet and cost of lumber from nominal sizes, per piece and in total.

Kalku is coming to iPhone and Android

The app has these ten and 215 more, a feet-inch-fraction keypad with construction keys, live 3D previews, and saved jobs you can share as a PDF. It works with no signal. Free, with no ads and no account.

Coming soon

The same formulas as the app

These calculators are not a web imitation of Kalku: they run its formulas, ported line for line from the app and tested against the app's own answers. Lengths are kept in inches inside, as in the app, and converted only for display, so a job typed in feet and inches and the same job typed in metres give the same result. Bag counts and sheet counts are rounded up the way the app rounds them, without buying an extra bag for a rounding error.

Every calculation runs on this page, there is no account, and the numbers you type are never stored on a server. The address bar keeps them once you change something, so a link reopens the same job: send it to a client, a supplier or the crew.

What the browser cannot do

A web page needs a signal, forgets your stored sizes and your jobs, and has no keypad that thinks in feet and inches. That is what the app is for: Kalku keeps your riser height, stud spacing and material densities, saves every calculation with a note, draws it in 3D and works on a roof with no reception.

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