Variation Order Cost Calculator
Full cost of a variation and the change against the original rate.
Quick answer
With the default inputs: Variation quantity 500 · New rate 145 CNY · Original rate 120 CNY etc.Total variation cost 87907 CNY
Edit the inputs below to recalculate.Inputs
Result
Total variation cost
87907CNY
| Direct cost | 72500CNY |
| Preliminaries | 5800CNY |
| Levy | 2349CNY |
| Pre-tax subtotal | 80649CNY |
| Tax | 7258CNY |
| Cost at original rate | 60000CNY |
| Change against original | 27907CNY |
| Percentage change | 46.5% |
| All-in rate | 175.81CNY |
The first rule of valuation is to use an applicable rate, then a similar one, and only re-rate when neither exists — so a new rate must come with a build-up. Where the quantity deviates by more than 15%, codes allow the rate to be adjusted: the excess above 15% may be priced lower, and after a cut beyond 15% the remainder may be priced higher.
Reverse: known result, work out one input
Enter a target result; the other inputs stay fixed and this one is worked out.
Formula
| Direct cost | quantity × new rate |
| Preliminaries | direct × rate |
| Levy | (direct + preliminaries) × rate |
| Tax | subtotal × rate |
| Total | direct + preliminaries + levy + tax |
| Change | total − quantity × original rate |
500 units at a new rate of 145 against 120, with 8% preliminaries, 3% levy and 9% tax: 72500 direct, 5800 preliminaries, 2349 levy, 80649 pre-tax and 7258 tax — 87907 in total, 12907 above the original rate.
How to work it out
- Confirm the variation is valid first: is there a design change notice, a client instruction or a supervisor's confirmation? Verbal instructions do not count unless written up the same day.
- Direct cost D = varied quantity × new unit rate. Measure the quantity as actually executed rather than estimating from drawings — a variation's value rests on accurate measurement.
- Preliminaries P = D × rate (typically 5-10%). Additional scaffolding, formwork and plant caused by the change come from here.
- Statutory fees L = (D + P) × 2-5%; tax T = (D + P + L) × 9%.
- Total C = D + P + L + T; the movement against the original rate is Δ = C − quantity × original rate, positive for an increase.
- Present a comparison table of old and new rates, quantities and totals, supported by photographs and measurement records. Figures without evidence still get cut at audit.
Where it goes wrong
- Applying the original contract rate mechanically. Where quantity moves more than ±15%, the code allows the rate to be adjusted because the amortisation base has changed — using the old rate can work against you.
- Computing preliminaries as a flat percentage of direct cost. If the variation extends the programme, the extra scaffolding, crane time and management far exceed 8%, and a separate time-related claim is needed.
- Ignoring the effect on work already done. If a change requires demolishing and rebuilding completed work, the demolition, rework and delay must be costed separately — not just the new element.
- Issuing a confirmation that says only that the situation is true, with no quantity or price. Such a record is worthless at settlement because it cannot be valued. State location, quantity, rate and date, signed by all parties.
Material and cost
Variations are priced three ways: an applicable contract rate, an analogous rate adjusted, or a build-up from quota or market rates where neither exists. Preliminaries 5-10%, statutory fees 2-5%, tax 9%. On variation-heavy projects the total can reach 10-20% of contract value — the main source of both profit and loss.
On site
- Timeliness matters most. Most contracts require submission within 14 days of the event, after which the claim lapses. Keep a variation register and review it weekly.
- Demolition and rework are the items most often disallowed. Photograph, video and count before demolition, with supervisor and client confirmation on site — retrospective sign-off rarely survives.
- The negotiating room on rates lies in the analogous-rate route. Where no exact match exists but the process is similar, split into material and labour and adjust — easier to agree than forcing a quota item.
- Submit variations and claims separately. A variation adjusts the contract; a claim compensates for matters outside it, such as suspension, acceleration or price escalation. Bundling them invites a blanket reduction.
Basis
- GB 50500-2013 Code of bills of quantities and valuation for construction works, contract price adjustment
- GF-2017-0201 Model construction contract, clauses on variations and claims
- GB 50854-2013 Standard method of measurement for building and decorative works
FAQ
Why do variations always get cut?
Because three things are missing: the instruction showing who ordered the change, evidence it happened — photographs, inspection records, delivery notes — and the build-up showing why that rate. Auditors work on no instruction, no claim; no evidence, no measurement; no build-up, no price. The classic mistake is doing the work first and signing afterwards, when the client is no longer in a hurry and the leverage has flipped.
When can a rate be re-priced?
Three cases: no identical or similar item exists in the bill; the quantity changes by more than 15% so the rate becomes unreasonable at the new volume; or a design change alters the method or specification materially. Otherwise the original rate stands. Re-pricing needs a labour, material and plant build-up, and auditors check consumption and market rates line by line, cutting anything inflated.
How does a site instruction differ from a design change?
A design change is a drawing revision issued by the designer and confirmed by the client, with formal paperwork; a site instruction records small or temporary work on the spot — hitting an obstruction, temporary propping, acceleration measures. Both are valued at settlement, but site instructions carry a higher evidential bar because they confirm after the event, so they are the first thing questioned in audit. Sign them the same day, with photographs.
Cite this page
Use this format in reports, method statements or coursework. The link is permanent.
Building Calculator. Variation Order Cost Calculator. 2026-10-25. https://jianzhujisuan.com/en/variation-order
Results are estimating aids only and are not a design basis. Construction and final accounts must follow the drawings, the applicable standards and an approved method statement. Anything affecting structural safety, shoring or falsework must be checked by a suitably qualified engineer.