Shed Base Estimator

Calculate concrete and ground preparation materials for a shed base or slab.

Shed base materials for a 4m by 3m base

For a shed base measuring 4 metres by 3 metres, this estimate includes concrete, hardcore and damp proof membrane allowance using the default build-up shown below.

Base area12.00 m²
Concrete1.32 m³
Hardcore2.64 tonnes
DPM allowance13.20 m²

Base length (m)

Base width (m)

Concrete depth (mm)

Hardcore depth (mm)

Wastage (%)

Results - Shed Base Estimator

Base area12.00 m²
Concrete1.32 m³
Hardcore2.64 tonnes
DPM allowance13.20 m²

How this shed base estimator works

It calculates the slab area, concrete volume, sub-base volume and a practical DPM allowance for common shed and outbuilding bases.

Frequently asked questions

The Shed Base Estimator gives a quick estimate for a project sized at 4m by 3m using the default assumptions shown on the page.

For most jobs you will need length and width. The calculator then uses those figures to estimate the materials shown in the results.

A small wastage allowance is often sensible because cuts, breakages, uneven ground and product differences can affect the final quantity needed.

Yes, the calculator is set up for typical UK-style measurements and practical estimating assumptions, but final quantities should still be checked before ordering.

It is designed as a practical planning tool and should be checked against the exact product specification, build method and site conditions before ordering.