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Groundworks · m³ · t · loads
How much muck will I dig out, and how many loads is that?
Dig volume, what it turns into once it is out of the ground, and how many lorries that is. Bulking is the bit that catches people out — a cubic metre of clay in the ground is a cubic metre and a third in the wagon.
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
- Dig volume =
L × W × Dplus any extra pits or steps - Weight =
dig volume × in-situ density— the density before it is disturbed - Bulked volume =
dig volume × (1 + bulking %)— broken ground takes up more room - Grab and tipper loads go by weight because that is what the haulier charges; skips go by bulked volume because that is what fills the box
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 |
|---|---|---|
| Grab lorry payload | 14 t | Typical 8-wheel grab. Check with your haulier — some run at 12 t on soft island roads. |
| Tipper payload | 18 t | 8-wheel tipper. A 6-wheeler is nearer 12 t. |
| Skip volume (8 yd) | 6.1 m³ | An 8-yard builder’s skip. A 6-yard is 4.6 m³, a 12-yard is 9.2 m³. |
| Fill level of skip | 85 % | Nobody fills a skip to the brim and they will not take it over the lip. |
A worked example
With the defaults the page opens on:
- How long is the dig? 12 metres
- How wide is it? 8 metres
- How deep is it? 0.9 metres
- Any extra to dig out? 0 cubic metres
- What is the ground? Topsoil / made ground
In the ground
- Dig volume: 86.4 m³ — L × W × D + extras
- Weight: 155.52 t — volume × 1.8 t/m³
Once it is out
- Bulking: 25 % — how much it swells when dug
- Bulked volume: 108 m³ — dig volume + 25%
- Grab lorry loads: 12 loads — by weight: 155.5 t ÷ 14 t payload
- Tipper loads: 9 loads — by weight, 18 t payload
- 8-yard skips: 21 skips — by bulked volume, filled to 85%
Change any figure above and every line recalculates; the small print under each row is the sum that produced it.
Questions people ask
What is bulking and why does it matter?
Ground takes up more room once it is dug. Clay bulks by about 30%, so a cubic metre in the ground is a cubic metre and a third in the wagon. Skips are filled by bulked volume, so ignoring it under-orders skips.
Are grab loads worked by weight or volume?
By weight, because that is what the haulier charges against a payload. Skips are worked by bulked volume, because that is what fills the box. The calculator does both.
How heavy is a cubic metre of clay?
About 1.9 t in the ground. Topsoil is nearer 1.8, sand and gravel 2.0, rock 2.3. Picking the material sets the density and the bulking together.
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.