Concrete · Gravel · Topsoil

Material calculators that show their working

Work out how much concrete, gravel or topsoil a job needs — with the density figures, bag yields and conversions written out so you can check the answer yourself.

Concrete CalculatorCalculate how much concrete a slab, footing, column or circular pad needs — in cubic yards, and in the number of bags that works out to.Gravel CalculatorCalculate how much gravel, crushed stone or crusher run a job needs — in cubic yards, and in the US tons a supplier will actually invoice you for.Topsoil CalculatorCalculate how much topsoil, compost or bed mix a lawn or garden bed needs — in cubic yards, which is how soil is quoted and delivered.

Why the numbers here are different

Most material calculators give you a number and nothing else. You cannot see which density they assumed, whether they added a waste allowance, or why the figure differs from what your supplier quotes. When the answer is wrong you find out on delivery day.

These calculators publish the numbers they use. Every density range, bag yield and conversion factor is printed on the page with a named source, and each one shows a worked example you can repeat on paper. If our figure disagrees with your supplier's, you can see exactly where the difference comes from.

Sources on the page

Each row of a data table says where its figure comes from, so you can open the document and check it.

A worked example

Every calculator includes a worked example you can repeat on paper and compare with the tool.

No false precision

Where published densities for a material differ, the weight shows that spread instead of one falsely exact number.

Guides

The questions that come before and after a quantity calculation.

Checking Topsoil and Compost Before the Truck Tips ItThe properties a topsoil specification makes you measure, what a texture class name really claims, and the one failure mode you have to test for yourself.Why the Yard Split Your Order Into Two LoadsThe federal axle and gross weight limits, the bridge formula and the state spring thaw rules that decide whether your order arrives on one truck or two.

Why the calculated figure is never quite the order figure

Three things move the real number. Subgrade: ground that has been over-excavated or left soft absorbs more than the nominal dimensions suggest. Compaction: loose aggregate settles, so the volume you order is larger than the volume you end up with. Supplier increments: ready-mix is sold in quarter-yard steps and bulk aggregate by the ton, so you round up to how the material is actually sold, not to how it was calculated.

Each calculator has a waste allowance you can set, and each page explains what allowance is normal for that material and why.

How these pages are made

Figures are printed on the page that uses them with the source named, so you can open the document and check. Every row of a calculator's data table says where its figure comes from: a named document, with the edition and section wherever the document has them, or a plain 'Not sourced' or 'Arithmetic' where no document gives the figure. The About page explains how the pages are checked before they go up.

The calculators are plain client-side arithmetic. No data leaves your browser and nothing is stored. If you find a figure you think is wrong, corrections are welcome.