How Much Concrete Do I Need for a Shed Base?

Worked figures for common UK shed sizes, laid 100mm deep in a 1:5 mix.

Page last reviewed 26 October 2026 by the UkToolCalc team

An 8×6ft shed base (2.44 × 1.83m) at 100mm deep needs about 0.47m³ of concrete: 7 bags of cement and 0.8 tonnes of all-in ballast (one 850kg bulk bag), with 5% extra included.

Work out your own in the Concrete calculator

0.47m³for an 8×6ft base at 100mm
1:5cement to all-in ballast
100mmconcrete on 75–100mm of MOT
+5%for uneven ground

Concrete for common shed sizes

100mm deep, 1:5 mix, 5% extra included. Cement in 25kg bags.

Shed size	Base (m)	Concrete	Cement	All-in ballast
6 × 4 ft	1.83 × 1.22	0.23 m³	4 bags	0.40 t (one bulk bag)
8 × 6 ft	2.44 × 1.83	0.47 m³	7 bags	0.80 t (one bulk bag)
10 × 8 ft	3.05 × 2.44	0.78 m³	11 bags	1.33 t (two bulk bags)
12 × 8 ft	3.66 × 2.44	0.94 m³	13 bags	1.60 t (two bulk bags)

The sum

Concrete (m³) = length (m) × width (m) × depth (m) × 1.05 8×6ft: 2.44 × 1.83 × 0.1 × 1.05 = 0.47m³

Under the concrete you also need a compacted sub-base: the MOT Type 1 calculator works out the tonnes. The shed base planner puts the dig, sub-base and concrete in one list.

Frequently asked questions

How thick should a concrete shed base be?

100mm of concrete on about 75–100mm of compacted MOT Type 1 is normal for garden sheds. Go to 150mm for heavy workshops, log cabins or soft ground.

Should the base be bigger than the shed?

Make it the size of the shed's floor or a little smaller (about 50mm in on each side), so rain running off the walls drips onto the ground, not onto the base.

Is ready-mix worth it for a shed base?

Usually not below about 1m³, because many suppliers have a minimum load. Mixing a small base by hand or with a hired mixer is often cheaper.

Related calculators

Concrete Calculatorm³ of concrete, cement bags and ballast for slabs, footings and post holes.

MOT Type 1 Sub-Base CalculatorTonnes and bulk bags of sub-base for patios, paths and driveways.

Excavation & Muck-Away CalculatorDig volume, bulked spoil, tonnes and skips or grab lorries to remove it. Concrete shed base plannerDig-out, MOT Type 1 and concrete for a solid shed or garden-room base.