Loose material compacts down — over-order a little so you don't run short.
All-in ballast is a pre-blended mix of sharp sand and 20mm gravel for making concrete, and also serves as bulk fill. It's sold loose by the tonne or in bulk bags. Enter your area and depth to size the order.
How to use this calculator
- Measure the area in square metres.
- Set the depth you need to fill or the slab thickness.
- Leave a small wastage allowance for over-dig and losses.
- Get delivered quotes for the tonnage from local yards.
How we work this out
We take your area and finished depth, work out the volume in cubic metres, then convert to weight using a loose delivered density of 1.8 tonnes per cubic metre for All-in ballast — the figure used across the UK trade. The compaction and wastage allowance is added on top so you don’t run short. Bulk-bag counts assume a standard 850 kg dumpy bag.
Delivered densities and coverage vary with grade, moisture and how hard the material is compacted, so these figures are a working estimate to size your order — always confirm the exact quantity and price with your supplier before buying. Our team reviews the density figures and guidance periodically; this page was last reviewed on 12 July 2026.
Frequently asked
How much ballast per square metre?
At 100mm depth, about 0.18 tonnes of ballast per square metre.
How much ballast for 1m³ of concrete?
Roughly 1.9 tonnes of all-in ballast plus cement makes about a cubic metre of general-purpose concrete.