UK paving calculator
Subbase Calculator UK
Use this UK subbase calculator to estimate MOT Type 1 or compactable sub-base for block paving, patios, and paths. Enter area and depth in the calculator below, or use the table for quick tonnes and bulk bag estimates.
Quick answer
- 10 m2 at 100 mm depth needs about 1.10 m3 or 2.20 tonnes of sub-base after 10% allowance.
- 20 m2 at 100 mm depth needs about 2.20 m3 or 4.40 tonnes.
- An 850 kg bulk bag estimate rounds up because partial bulk bags are not orderable.
UK sub-base estimates
| Area | Depth | Cubic metres | Tonnes | 850 kg bulk bags |
|---|---|---|---|---|
| 10 m2 | 100 mm | 1.10 m3 | 2.20 t | 3 |
| 20 m2 | 100 mm | 2.20 m3 | 4.40 t | 6 |
| 30 m2 | 100 mm | 3.30 m3 | 6.60 t | 8 |
| 40 m2 | 100 mm | 4.40 m3 | 8.80 t | 11 |
| 20 m2 | 150 mm | 3.30 m3 | 6.60 t | 8 |
Assumes 10% allowance, 2.0 tonnes per cubic metre compactable sub-base, and 850 kg bulk bags.
Interactive estimator
Paver Base calculator
Example 10x10 patio: base is about 1.36 cu yd, 2.17 tons, or 74 half-cubic-foot bags.
Enter your own length, width, depth, density, and bag size to create a supplier order.
How to calculate sub-base
Multiply area in square metres by compacted depth in metres, then add an allowance for compaction, trimming, and ordering buffer. For 20 m2 at 100 mm, the compacted volume is 2.0 m3 before allowance and 2.20 m3 after a 10% allowance.
Most UK suppliers quote MOT Type 1 or sub-base by bulk bag, tonne, or loose load. Use the tonnes result for loose deliveries and the bulk bag count for merchant orders.
MOT Type 1 and sub-base depth
A pedestrian patio or path often uses around 100 mm of compacted sub-base as a planning depth. Driveways, poor ground, or areas with vehicle loading may need 150 mm or more and should be confirmed locally.
This is a planning estimate, not an engineering specification. Confirm ground conditions, drainage, and product density with your supplier or installer.
Helpful next step
Use the main paver material calculator when you need a complete order list. Use the UK pages when your supplier quotes sub-base, MOT Type 1, sharp sand, or block paving materials.