Construction Calculators

Every calculation on this shelf answers the same practical question: how much do I need to buy, and what will it cost? Getting it wrong is expensive in both directions — a second delivery costs a day, and surplus concrete cannot be returned.

Almost all of them start from area, which is why the square footage calculator is the most used tool here. It handles rooms of any shape, adds several together, and converts between square feet, square metres and square yards. Once you have area, the rest is depth, coverage and a waste allowance.

The volume tools — concrete, gravel, sand and mulch — multiply area by depth and then translate into what suppliers actually sell: cubic yards, tonnes, truckloads or bags. That last step is where mistakes happen, because a cubic yard of gravel weighs roughly 1.4 tonnes while a cubic yard of mulch weighs a fraction of that, and both are ordered by volume.

The surface tools — paint, flooring, tile and roofing — work from area to units. Paint subtracts doors and windows before applying coverage and coats. Flooring and tile convert to whole boxes including waste, because you buy boxes. Roofing applies a pitch multiplier to the building footprint, since a 6:12 roof has about 12% more surface than the ground it covers.

The odd one out is the electricity cost calculator, which turns wattage and run time into kilowatt-hours and then into a daily, monthly and annual bill. It lives here because it is the household question people ask most often after they have finished measuring things.