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Groundworks · t · bags
How much gravel or topsoil do I need?
Gravel, shingle, topsoil, sharp sand or bark for an area at a depth, by weight, with bulk bags. The density is the material’s own and varies by quarry - change it to the figure your supplier gives.
Measure it
Every box has its own unit next to it.
Change the unit beside any box and the number converts. The (i) beside each question says what the box wants and where the figure usually comes from. Anything marked per cent is a percentage of the quantity above it.
Check the rates
Rates and assumptions used
These are the figures the calculator works to. Change any of them and the order list updates — your merchant’s pack sizes and your own waste allowances beat the defaults every time.
Order list
The orange figure is the one you order to. Highlighted rows are the other numbers you order to. The small print under each row is the sum that produced it, so you can check it against your own take-off. Amber rows are warnings, not quantities.
How this one works
- Volume =
area × depth × (1 + waste %) - Weight =
volume × density - Bulk bags =
weight ÷ bag weight, rounded up
The figures the calculator works to. Every one can be changed in step 2, and your merchant’s pack sizes and your own waste allowances beat these defaults every time.
| Rate | Default | Why |
|---|---|---|
| Gravel density | 1.6 t/m³ | Loose gravel or shingle. Your supplier’s figure is the one to use. |
| Topsoil density | 1.4 t/m³ | Loose and dry. Wet topsoil is heavier. |
| Sharp sand density | 1.6 t/m³ | Loose. |
| Bark density | 0.3 t/m³ | Bark is often sold by volume - see the volume line. |
| Bulk bag weight | 0.85 t | A standard merchant bulk bag. |
A worked example
With the defaults the page opens on:
- How long is the area? 10 metres
- How wide is it? 4 metres
- Any odd bits to add on? 0 square metres
- Which material? Gravel or shingle
- How deep? 50 millimetres
- How much spare? 5 per cent
Material
- Area: 40 m² — L × W + extra area
- Depth: 50 mm
- Volume: 2.1 m³ — area × depth, +5%
- Weight to order: 3.36 t — × 1.6 t/m³
- Bulk bags: 4 bags — 3.4 ÷ 0.85 t a bag
Change any figure above and every line recalculates; the small print under each row is the sum that produced it.
Questions people ask
How much gravel do I need?
Area × depth, plus waste, × the gravel’s density. A 10 m × 4 m path at 50 mm with 5% spare is 2.1 m³ - 3.36 t at 1.6 t/m³, or four 0.85 t bulk bags.
What density should I use?
The one your supplier gives: it varies by quarry and by how wet the load is. The calculator starts gravel and sharp sand at 1.6 t/m³, topsoil at 1.4 and bark at 0.3, and each can be changed.
How deep should topsoil be?
The hint gives common figures - 100 to 150 mm for a new lawn, deeper for a planted bed. The depth is your choice; this works out the quantity at it.
Calculators for the same job
Doing this for a whole job rather than one wall? SiteLedger keeps the valuations, supplier statements, invoices and variations against the project they belong to.
Read before you order. These work out quantities, not structural design — spans, lintels, rebar and foundation depths need an engineer and Building Control sign-off. Waste allowances are defaults, not promises: awkward cuts, long runs and bad weather all eat more than 5%. Where a merchant sells whole packs, the figure is rounded up to whole packs.