Free calculators for real-world projects
Work out how much to buy, what it will cost and what size you need. Every formula is shown and every result is checked against published references.
Home & Garden
View all →Concrete CalculatorWork out how much concrete you need in cubic yards or cubic metres, and how many 40, 60 or 80 lb bags to buy, for slabs, footings and post holes.Gravel CalculatorFind how many cubic yards and tons of gravel, crushed stone, pea gravel or sand you need for a driveway, path, patio base or drainage area.Mulch CalculatorCalculate how much mulch you need in cubic yards, cubic feet or bags for garden beds and around trees, at any depth.Topsoil CalculatorWork out how much topsoil you need in cubic yards, tons or bags for a new lawn, garden bed, raised bed or top-dressing.Asphalt CalculatorEstimate how many tons of hot-mix asphalt you need for a driveway, parking pad or patch from the area and compacted thickness.Square Footage CalculatorCalculate square footage for rectangles, L-shaped rooms, circles, triangles and trapezoids, with square yards, square metres, acres and cost.Roofing CalculatorEstimate roof area, roofing squares, shingle bundles and underlayment from your house footprint, roof pitch and overhang.Roof Pitch CalculatorConvert roof rise and run into pitch (x/12), angle in degrees, slope percentage and the pitch multiplier, or work back from an angle.Pool Volume CalculatorCalculate how many gallons or litres of water your pool holds, for rectangular, round, oval and kidney-shaped pools, plus how long it takes to fill.Pool Salt CalculatorCalculate how many pounds or kilograms of salt, and how many bags, you need to reach the right salt level (ppm) for a saltwater chlorinator.Septic Tank Size CalculatorEstimate the minimum septic tank size for your house from the number of bedrooms, and how often it will need pumping for your household.BTU CalculatorFind the BTU rating for a room air conditioner, mini-split or heater from the room size, ceiling height, sun exposure, occupants and climate.
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