A list of free building calculators for NZ builders. Pick one: concrete, decking, fence, framing, GIB, insulation, tiles, roof area, stairs and more.
Sixteen free calculators for NZ residential work. No signup, no card. Most count material for one trade: boards, sheets, bags, batts, lineal metres. The rest set out geometry instead: a stair flight, a balustrade run, a fall or gradient, and a cut list that turns pieces into lengths to order. All of them show the working, so you can check the number rather than trust it.
Decking calculator: board rows, lineal metres, fixings and a cut list that places every join on a joist centre. Wall framing calculator: studs, plates, nogs and dwangs at the centres you set. Stair calculator: rise, going and tread count for a straight flight.
Post hole calculator: hole volume and how many bags of premix it takes, which is the one most often guessed and most often wrong by a whole pallet. Fence calculator: posts, rails, palings and the concrete to go with them.
Concrete calculator: cubic metres for a slab or pad, and the bag count if you are mixing on site rather than ordering a truck. Roof area calculator: true roof area from the plan footprint and the pitch, which is not the same number as the floor area under it.
Cladding calculator: board coverage for a wall area. Spouting calculator: lineal metres of gutter and downpipe from the roof run.
GIB calculator: plasterboard sheets for walls and ceilings, counted in sheets because that is how it is sold. Insulation calculator: batt coverage for a wall, ceiling or floor area. Tile calculator: tiles and adhesive for a floor or wall. Paint calculator: litres to paint the walls of a room.
Balustrade calculator: even post bays with no stub at the end, the baluster count, and the real clear gap to mark between them. It uses the same even-division solver as CostMate's deck engine.
Cut list calculator: the one that fixes an ordering mistake rather than a counting one. Twenty pieces at 2500mm is fifty lineal metres, but 2500 only comes out of a 6.0m length twice; order by the metre and you are short. This packs the actual pieces into actual lengths and gives you the cut plan.
Fall and gradient calculator: 1:60, 1.67%, 0.95° and 16.7mm per metre are one slope written four ways. Convert between them and get the drop over a measured run, which is what you set a string line to.
Every calculator here answers how much to order. None of them answers whether a member is big enough to do its job. Spans, member sizes, fixing schedules and bracing are design decisions that belong to your consented plans, your designer's B1 (Structure) work, or an engineer for your site.
If you want the whole job priced rather than one trade counted (labour hours, materials, assumptions and exclusions on one document) that is what CostMate estimates do, and there is a free plan on the pricing page.
Check every quantity against your own plans and your supplier's actual stock sizes before you order.