Compaction Factor Calculator

How the compaction factor calculator works

Adjusts bulk material volume for compaction factor after laying. The calculator takes a loose volume and the material, divides by the material's bulking factor, and returns the settled in-situ volume with the shrinkage that goes with it. Every figure is an estimate — site conditions always move the final number.

Typical UK drainage and earthworks wastage

Excavated soil typically bulks up by around 15–35% when lifted, depending on the material, so skip capacity fills faster than the in-situ volume suggests. A rough 1.25× allowance is common for muck-away skip filling, which is a separate figure from the per-material bulking factor this tool divides by. These are trade-typical values rather than a site test, so they shift with moisture, layer depth and compaction effort.

What this tool does not do

It does not replace a professional quote, factor regional pricing, assess structural adequacy, or confirm Building Regulations compliance. Those remain the responsibility of a suitably qualified designer, surveyor, or your building control officer.

On-site considerations for compaction factor

Excavations over 1.2 m deep typically need shoring or battered sides, and HSE guidance on trench collapse applies. Buried services are located with a CAT scanner before digging.

Building Regulations and compliance

Foul and surface water drainage to a public sewer is governed by Approved Document H and Sewers for Adoption. Soakaways need a permeability test (BRE 365) to size correctly. A pre-application enquiry to the local authority can give early clarity, which tends to be less costly than retrospective correction.

Before you order

Plastic drainage pipe is commonly supplied in standard 3 m or 6 m lengths with integral seal joints, and cutting short lengths on site wastes material and fittings. Cross-checking the calculator’s output against a supplier quote helps catch differences in pricing assumptions — a quote listing exact product specifications (grade, finish, batch number) with confirmed delivery timescales is easier to reconcile against a programme.

Adjusting the defaults

Every input in this calculator is editable. Enter your own loose volume and choose the material — the output recalculates instantly. If the default does not match your job, your own numbers always override it.

Using this compaction factor calculator alongside other BuildMetricLab tools

This calculator works best as part of a planning workflow. Pair the quantity with our project contingency, labour-hours, and material-cost calculators to build a complete estimate before you pick up the phone to a supplier. All BuildMetricLab tools run entirely in your browser — no sign-up, no data sent anywhere, and every formula is shown on-page so you can audit the maths.