What it does
Before ordering gravel, sand, topsoil or mulch, you need to know how much. This calculator adds up the areas you are covering, multiplies by the depth and gives the volume in cubic metres, cubic yards and cubic feet. It also gives the weight in tonnes, US tons, kilograms and pounds, and a count of bags.
Everything runs in your browser and nothing is sent anywhere. If the job includes a concrete slab or a deck, the concrete calculator and deck calculator work out those parts.
How to use it
- Choose metric or imperial. Switching converts the numbers already typed.
- Type the size of each area. “Add an area” adds another shape; “Remove” takes one away.
- Type the depth, pick the material and a bag size. “Reset” brings back the example.
What each setting does
- Units: metres with depth in millimetres, or feet with depth in inches.
- Shape: a rectangle (length x width), a circle (diameter) or a triangle (base x height / 2).
- Extra for settling and spill: adds a percent to the volume. Gravel and soil settle when compacted.
- Material: fills in an approximate density: gravel, crushed stone and sand about 1.6 t/m³, topsoil 1.3, bark mulch 0.4.
- Density: edit it if your supplier gives a figure.
- Bag size: weight bags (25 kg, 20 kg, 50 lb, 40 lb) are counted from the weight; volume bags (1, 2 or 3 cu ft) from the volume. The count rounds up.
Worked example
A path 5 m long and 2 m wide, 75 mm deep, covers 10 m². The volume is 10 x 0.075 = 0.75 m³ (0.981 yd³). Gravel at 1.6 t/m³ weighs 0.75 x 1.6 = 1.2 tonnes, which is 48 bags of 25 kg.
In imperial, a bed 9 ft by 9 ft, 4 in deep, needs 27 cu ft, which is exactly 1 cubic yard. In 3 cu ft bags of mulch that is 9 bags.
FAQs
Is a ton the same as a tonne? No. A tonne is 1,000 kg; a US ton is 2,000 lb, about 907 kg.
Why does my supplier’s figure differ? Density depends on the stone size, moisture and how loosely it is loaded.
Where the numbers come from
- Area and volume formulas and unit conversions (1 ft = 0.3048 m, 1 lb = 0.45359237 kg, 1 US ton = 2,000 lb): standard definitions, fibub's own working.
- Densities (gravel, crushed stone and sand about 1.6 t/m³, topsoil about 1.3, bark mulch about 0.4) are rounded typical figures chosen by fibub; real loads vary with moisture and grading, so ask your supplier.
Standard scientific values, such as constants, atomic weights and melting points, are facts found in every textbook; we name where ours were checked. If you are an author or publisher and want a value, a credit or a table changed or removed, tell us and we will act quickly.
Last updated 2026-11-10.