Estimates, not advice
The calculators on BuildMaths turn the dimensions you enter into estimated quantities using typical product sizes, coverage rates and allowances. They are general information. They are not advice about your project, they do not know your site, and they are not a substitute for the judgement of a builder, engineer or supplier who does.
Not structural design
Nothing on this site sizes a footing, a slab, a beam, a joist, a post or a retaining wall. Where a calculator mentions a thickness, a depth or a spacing, it is a common starting point for the quantity calculation only. Structural decisions come from the National Construction Code, the relevant Australian Standards, the manufacturer's span tables and, where required, an engineer's design for your site and soil.
Check the product
Product sizes, bag yields, sheet covers and coverage rates change, and vary between manufacturers. The assumptions used are listed on every calculator. Where they differ from the product you are buying, the product's own figures apply. Confirm the final order with your supplier.
Permits and regulations
Whether your work needs a building permit, a planning permit, an engineer, a registered builder or an owner-builder certificate depends on where you are and what you are doing. Mentions of permits on this site are general and Victorian; check with your council and building surveyor.
Liability
To the extent permitted by law, BuildMaths and its publisher are not liable for any loss, damage, cost or expense arising from the use of, or reliance on, information or calculations on this site, including material ordered short or over, or work carried out on the basis of a figure shown here. Nothing on this page excludes any guarantee, right or remedy that cannot be excluded under the Australian Consumer Law.
Errors
We try hard to get the numbers right and we correct errors when they are reported. If you find one, please tell us.