Tools · Variations
Price the variation,
and see what it does to the job.
List what the variation costs you, apply your own markup or margin to each kind of cost, add any administration charge and GST, and read the client price. Enter the job it sits on and the calculator shows the job margin before and after. No percentages are supplied; every rule is yours.
Written by Brad Caldon, Founder, VIABUILD. Licensed builder (NSW) · Registered Building Practitioner (Class 1 to 9) · B.Construction Management (Hons) · Last reviewed 20 September 2026
01 / The calculator
Price the variation
One cost line to start. The pricing rules, the administration charge, GST and the job figures each add a line to the result.
The variation price
Enter at least one cost line to start. The percentages, the administration charge, GST and the job figures each add a line here.
02 / Reading the result
The variation and the job are two different questions
The first question is whether the variation makes money, and the top of the result answers it: the price less your cost is the gross profit, and the margin and markup lines show that profit against the price and against the cost. The second question is what the variation does to the job, and that is the pair of lines at the bottom. A job at a healthy margin can absorb a dozen small variations priced a little too keenly and finish thinner than the estimate said it would, with no single decision to point at.
Pricing per kind of cost is what most builders actually do, even if the rule lives in their head. A subcontract quote already carries the trade's margin, so a lower percentage on it is common; own labour and materials carry the builder's full overhead recovery. The margin and markup reference explains why the two percentages describe the same dollars differently, and the scope creep reference covers the variations that never get priced at all.
03 / Common mistakes
Where variation pricing goes wrong
- Pricing from the subcontract quote alone. The quote is the trade's cost to you. Your supervision, documentation and risk sit on top of it, and a variation passed through at cost is work done for nothing.
- Applying the job margin as a markup. A 20% margin and a 20% markup are different prices. Check the toggle matches the rule you mean.
- Doing the work before the approval. The price this calculator produces is worth nothing unless the client agreed to it in writing first. The managing variations guide is the sequence.
- Leaving variations off the claim. Approved variations are claimed with the stage they belong to. Unbilled variations are the commonest reason a job that felt profitable finished thin.
04 / FAQ
Common questions.
From cost up. Each item of extra work is costed the way the original estimate was, materials, own labour, subcontract quotes and plant, and the builder's pricing rule is applied to each line. Many builders apply different percentages to different kinds of cost, a higher one on own labour and a lower one on a subcontract quote that already carries the trade's margin, which is why the calculator asks for a percentage per category rather than one figure. A fixed administration charge for documenting the variation is common where the contract allows it. The result is the price the client is asked to approve in writing before the work is done.
Whichever your business actually uses, and the toggle exists because the two are not the same number. A markup is added to cost; a margin is a share of the price. A 20% markup on a $1,000 cost gives a $1,200 price and a 16.7% margin. A 20% margin on the same cost gives a $1,250 price. If your estimating software multiplies cost by a factor, that factor is a markup. The margin and markup calculator on this site converts between them. The result panel shows both figures for the variation as priced, so you can check the rule produced what you meant.
Because a variation can make money on its own and still weaken the job. If the job is running at a 20% margin and a variation is priced at a 10% margin, the job margin after the variation is lower than before, even though the variation itself is profitable. Enter the job contract sum and your current cost to complete and the calculator shows the margin before and after. It is the quickest way to see whether the pricing rule for variations is protecting the job or quietly diluting it.
The calculator shows the price both ways, ex GST and inc GST, at the rate you enter. Which figure goes on the variation document depends on how your contract states prices and how your accountant treats variations, so the rate is entered rather than assumed and the page gives no tax advice.
More than the price. The description of the changed work, the price and how it was arrived at, any effect on the completion date, and the client's written approval dated before the work starts, in the form your contract and state legislation require. The variation register template on this site tracks each one from request to approval, and the managing variations guide sets out the document, price, approve sequence. This calculator supplies one line of that document, the price, from your figures.
A credit variation runs the same way in reverse: the cost saved is the cost line, and the pricing rule decides how much of the saved margin is passed back. Contracts often deal with credits differently from additions, so read the variation clause before applying the same percentage in both directions. The calculator prices additions; for a credit, price the omitted work as if it were an addition and treat the result as the amount to credit, then check it against the contract wording.
05 / Keep reading
The references behind this calculator
The variations and pricing references, the register that tracks each one, the companion calculators, and the software that prices and approves variations on the job.
06 / Cite this
How to cite this page
To reference this page, use the wording below and link the page rather than copying it, so readers reach the current version. Corrections to hello@viabuild.au.
Citation
Brad Caldon, VIABUILD, Variation pricing calculator, https://www.viabuild.au/tools/variation-pricing-calculator, last reviewed 20 September 2026.
Or price it on the job, with the approval attached.
VIABUILD prices a variation from the job's own cost data, sends it to the client for a recorded approval, and carries the approved amount onto the next progress claim and into the forecast final cost without re-keying.