# Costing

Costing turns a quantity into money: multiply by rate, add preliminaries, apply overheads and tax. A unit rate is labour plus material plus plant plus management plus profit plus risk allowance, and each component has its own basis — apply the wrong basis and the whole rate drifts by more than 10%.

The other tools are about cash flow. VAT at the general rate or the simplified rate behaves very differently once input credit is considered; progress payments are made at the contract percentage but held back for retention (typically 3%) and recovered for mobilisation advance; variations are priced against an existing similar rate before a new rate is built up. These are the items that turn into disputes at final account, so price them before you negotiate.

- Category page: https://jianzhujisuan.com/en/c/costing
- Data checked: 2026-10-25

## Tools in this group

- [Cost per Square Metre Estimator](https://jianzhujisuan.com/en/cost-per-m2): Cost per m² and in total by structure, region and finish.
- [Concrete Cost Calculator](https://jianzhujisuan.com/en/concrete-cost): Material, pumping and the all-in rate per cubic metre.
- [Rebar Cost Calculator](https://jianzhujisuan.com/en/rebar-cost): Material, fabrication, fixing and the all-in cost per tonne.
- [Labour Cost Build-up Calculator](https://jianzhujisuan.com/en/labor-cost): Day rate build-up with overheads, levies and tax.
- [Formwork Cost Calculator](https://jianzhujisuan.com/en/formwork-cost): Amortisation, labour, support and the all-in rate per m².
- [Scaffolding Cost Calculator](https://jianzhujisuan.com/en/scaffold-cost): Rent by duration plus erection labour, giving total cost.
- [Construction VAT Calculator](https://jianzhujisuan.com/en/vat-calc): Output tax, input credit, VAT payable and surcharges.
- [Unit Rate Build-up Calculator](https://jianzhujisuan.com/en/unit-price): Build up an all-in unit rate from labour, material and plant.
- [Progress Payment Calculator](https://jianzhujisuan.com/en/progress-payment): Advance recovery, retention and the amount due this period.
- [Variation Order Cost Calculator](https://jianzhujisuan.com/en/variation-order): Full cost of a variation and the change against the original rate.

## Questions

### How do I estimate cost per square metre?

Total cost divided by gross floor area. Indicative ranges for the structure and finishes package run about 1200-1800 per m² for low-rise masonry, 1800-2600 for mid-rise frame-shear wall and 2200-3200 for high-rise shear wall. Location, specification and the number of basement levels matter more than the structural form, so correct against recent local settlements.

### What goes into a unit rate?

Labour, material including delivery and storage, plant and tools, overheads, profit and a defined risk allowance. Statutory fees and tax sit outside the unit rate. Under a bill-of-quantities approach the unit rate is one component of the all-in rate — do not double-count tax inside it.

### How is construction VAT calculated?

Under the general method, output tax is 9% of the net-of-tax income and input tax is recoverable. Under the simplified method, tax is 3% of the tax-inclusive income divided by 1.03, with no credit. Simplified treatment is available for labour-only and owner-supplied-material work; which is cheaper depends on how much input tax you can actually recover.