Drainage & Earthworks
Compaction Factor Calculator
Adjusts bulk material volume for compaction factor after laying
Updated 29 April 2026 · Live
What this tool does
Adjusts bulk material volume for compaction factor after laying.
People also use
How the compaction factor calculator works
Adjusts bulk material volume for compaction factor after laying. The calculator takes your dimensions and supplier rates, applies a standard UK trade formula, and returns a quantity with an indicative cost. Every figure is an estimate — site conditions always move the final number.
Typical UK drainage and earthworks wastage
Excavated soil bulks up 15–35% when lifted, so skip capacity fills faster than the in-situ volume suggests. Plan for a 1.25× factor when hiring away muck. Our defaults reflect common UK trade allowances — adjust upwards for non-standard geometry, downwards if your experience says so.
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 need shoring or battered sides — the HSE guidance on trench collapse is not optional. Check for buried services 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. When in doubt, lodge a pre-application enquiry with your local authority — early clarity is cheaper than a retrospective correction.
Before you order
Buy plastic drainage pipe in standard 3 m or 6 m lengths with integral seal joints. Cutting short lengths on site wastes material and fittings. Always cross-check the calculator's output against a supplier quote — ask for exact product specifications (grade, finish, batch number) and confirm delivery timescales against your programme.
Adjusting the defaults
Every input in this calculator is editable. Enter your own dimensions, supplier prices, and wastage allowance — the output recalculates instantly. If the defaults feel off for your region or project type, your own numbers always override them.
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.
Sources & methodology
Adjusts bulk material volume for compaction factor after laying. Uses UK trade defaults for wastage and density. Prices are illustrative April 2026 values; change them to match your supplier quote.
Frequently asked questions
Are compaction factor calculator results accurate enough to order materials?
Use them as a starting estimate only. Always verify the final quantity with your supplier or contractor before ordering — site conditions, wastage and cut-offs all affect the true figure.
What wastage percentage should I use?
The calculator defaults to the typical UK trade allowance for drainage & earthworks. Increase it for complex cuts, awkward shapes, or first-time DIY. Reducing the wastage below the default is not recommended.
Does this replace professional advice?
No. This tool is a planning estimator. For works that affect structure, Building Regulations, Party Wall, gas, electrics, drainage to a sewer, or similar, consult a suitably qualified professional.
Can I change the unit prices?
Yes — every price field is editable. Plug in your supplier's quote to get a total that matches your project.
Related tools
Calculators from other categories that planners often reach for next.