Trade & Construction calculators
Concrete, electrical, plumbing, tile, and building calculators
13 calculators · 2 guides
Trade calculators here are quantity and sizing aids for quoting and ordering: how much concrete a slab needs and how many bags that is, how many tiles including cuts, decking boards and joists, fence posts and rails, circuit load and breaker sizing, pipe flow, insulation values and heating or cooling capacity for a room.
They state the assumptions that drive the number, bag yields, waste allowances, spacing, standard efficiencies, because those are the levers that change an order by a pallet. None of them replace a licensed tradesperson, an engineer's certification, or the standard or code that governs the work.
Start with these in Trade & Construction
Roof Pitch and Rafter CalculatorConvert roof pitch between ratio and degrees, then get rafter length, ridge height and the true roof area including the slope factor.Trade & ConstructionConcrete Volume CalculatorCalculate how much concrete a slab, footing or path needs in cubic yards, cubic metres and bag counts, with a waste allowance and a delivery weight.Trade & ConstructionStair Rise and Run CalculatorWork out riser height, tread going, stringer length and pitch for a flight of stairs, and check the result against building code limits.Trade & ConstructionBrick and Block CalculatorWork out how many bricks or blocks a wall needs, with mortar, sand and cement quantities, for Australian, UK and US brick sizes.Trade & ConstructionTile CalculatorWork out tiles and boxes to order with the grout joint and wastage included, plus tile adhesive and grout quantities for floors and walls.Trade & ConstructionElectrical Load CalculatorWork out real and apparent power for single or three-phase circuits and the next standard breaker rating under NEC, AS/NZS 3000 or BS 7671 rules.Trade & Construction
Every Trade & Construction calculator
13 calculators
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- Concrete Slab Calculator (cubic metres and bags)Work out the cubic metres of concrete in a rectangular slab, the ready-mix order with a waste allowance, the equivalent 20 kg bag count, the mass and the cost.
- Concrete Volume CalculatorCalculate how much concrete a slab, footing or path needs in cubic yards, cubic metres and bag counts, with a waste allowance and a delivery weight.
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Guides for Trade & Construction
- 8 min readEssential Engineering Formulas and CalculationsKey formulas and calculation methods used in civil, mechanical, and electrical engineering.
- 9 min readRoof Pitch, Slope Factor and Ordering Roofing MaterialsWhy a roof is always bigger than the building under it, how pitch is quoted three different ways on the same job, and how to order materials without a second delivery.
Questions about trade & construction calculators
- How many bags of concrete are in a cubic metre?
- It depends entirely on the bag's yield, which is printed on the bag. As a working guide, a twenty kilogram bag of general purpose pre-mix yields roughly ten litres of set concrete, so about a hundred bags make a cubic metre. Anything beyond a couple of hundred litres is usually cheaper, stronger and far less work delivered pre-mixed. The calculator shows both the volume and a bag count so you can compare.
- Should I trust an electrical load calculation?
- Use it for planning conversations only. Real circuit design depends on the wiring rules in force where you are, cable size and length, installation method and grouping, voltage drop, diversity, protective device characteristics and earthing. In Australia this work is licensed. The calculation tells you roughly what scale of circuit you are dealing with, and a licensed electrician determines and certifies what is actually installed.
- Why do heating and cooling sizing results vary so much?
- Because floor area is only one input. Ceiling height, insulation, glazing area and orientation, air leakage, climate zone and how many people occupy the room change the load substantially. A quick per-square-metre estimate is fine for shortlisting a unit size; a room-by-room heat load assessment is what avoids an undersized system that runs flat out or an oversized one that short-cycles and never dehumidifies.