Building calculators that use the numbers builders use
Metric, Australian products, and the waste allowances a site foreman would actually add. Every calculator shows its working and its assumptions, so you can check it before you order.
Concrete and footings
- Concrete slab
Cubic metres, 20kg bags, mesh sheets and edge beams.
- Concrete for post holes
Bags per hole for fence, deck and pergola posts.
- How much does a 20kg bag make?
Bags to cubic metres, and the point where premix wins.
- Footings
Strip and pad footing concrete, plus trench mesh.
Timber and decking
- Decking boards
Square metres to lineal metres, boards, screws and joists.
- Paling fence
Posts, rails, palings, nails and concrete.
- Stairs
Risers, going and run, checked against the NCC.
- Stud wall
Studs, plates, noggins and lintels at 450 or 600.
- Weatherboards and cladding
Lineal metres, boards and fixings from the cover width.
Roofing
- Colorbond roof sheets
Sheet count and length from the roof plan and pitch.
- Roof area and pitch
True area, rafter, ridge, hips, gutter and barge lengths.
Bricks, blocks and walls
- Bricks
Bricks per square metre, pallets and mortar.
- Concrete blocks
Blocks per square metre and core fill.
- Sleeper retaining wall
Sleepers, posts, post length and concrete.
- Render
Bags of render by area and thickness.
- Paving
Pavers per square metre, bedding sand and road base.
Linings and finishes
- Plasterboard
Sheets by size, screws, compound and cornice.
- Paint
Litres and cans for a room, less doors and windows.
- Tiles
Tiles, boxes, adhesive and grout with waste.
- Insulation batts
Packs for walls and ceilings by pack coverage.
- Flooring
Packs or lineal metres, underlay and scotia.
Earthworks and landscaping
- Crushed rock, sand, soil and mulch
Cubic metres, tonnes and trailer loads.
- Excavation
Cut volume, bulking, tonnes, truck loads and machine time.
- Skip bins
Which bin size, and whether weight is the problem.
- Turf
Square metres, pallets, topsoil and fertiliser.
- Area of odd shapes
L-shapes, triangles, circles and trapezoids added up.
Money and project
- Builder margin vs markup
Cost to price, and why 20% markup is 16.7% margin.
- GST
Add or remove 10% the right way.
- Progress payments
Victorian contract stages in dollars.
- Charge-out rate
The hourly rate a trade business has to charge.
About these calculators
Most quantity calculators online are built for the American market, in feet and yards, with product sizes that do not exist here. These are built around Australian products and metric measurements: 20 kg bags, 762 mm corrugated sheet cover, 230 × 110 × 76 mm bricks, 2400 × 1200 mm plasterboard, R2.5 batts at 430 mm centres. Each one states what it assumes, shows a worked example, and tells you what a builder would actually allow on top of the raw number.
They are quantity estimators, not structural design and not a quote. Always check the final order with your supplier and, for anything structural, with your engineer's drawings.