Concrete calculator: cubic metres, bags of ballast and cement, or ready-mix

Enter the size of your slab, base or footing and pick a mix. The calculator gives the concrete volume in cubic metres and the ballast and cement bags to order.

Enter the slab or footing size (metres or mm) and we work out the concrete volume and the ballast, cement and water you'd need to mix it yourself.

Length

Width

Depth

Wastage

Mix strength

Concrete needed

2.52 m³(incl. 5% waste — 2.40 m³ net)

Ballast (all-in)6 bulk bags
Portland cement31 × 25kg bags
Water (approx.)416 litres

Mix on site or order ready-mix

For a bigger pour, get delivered concrete priced by local plants.

Get ready-mix quotes — 2.52 m³

Which works out cheaper?

This pour needs 6 ballast bulk bags and 31 cement bags. We fill in the cheapest prices from Price Planter — change any box to your own costs, including VAT. Quantity alone cannot tell us which is cheaper.

Ballast price per bulk bag (£, inc VAT)Cement price per 25kg bag (£, inc VAT)Site mixing extras (£) — mixer hire, a hand mixing, getting the bags to siteWe assume £0 — add mixer hire or paid delivery if you'll need them.Ready-mix total delivered (£, inc VAT)Plants price their own delivery — tap Get ready-mix quotes below, then put the best total here.

Finding today's bag prices…

Figures are nominal mixes — confirm the spec with your engineer or supplier before ordering.

How it works

1Measure the area — length, width and depth. A shed base is usually 100mm deep; a driveway or garage base is often 150mm.
2Pick your mix. A general-purpose 1:2:4 mix suits paths and bases; a stronger mix suits driveways and footings.
3Read the volume in cubic metres. That's the figure a ready-mix supplier will ask for if you'd rather order it delivered.
4Or read the bag quantities. The calculator converts the volume into bulk bags of ballast and 25kg bags of cement for mixing on site.
5Allow a little extra. Uneven ground eats concrete — most people order around 10% over for a base dug by hand.

Material prices for this job

Related calculators and guides

Now find the cheapest place to buy

Take your quantities across to Price Planter and compare them across UK builders' merchants — including whether splitting the order across two merchants works out cheaper.

Compare material prices

Volumes and bag quantities use typical trade conversion figures and are a guide only — confirm with your groundworker or ready-mix supplier before ordering.

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