THE NUMBERS, EXPLAINED
How to use this calculator.
Signed variations are already approved; balances do not establish the due date or payment entitlement.
Start with your inputs
Enter original contract sum (currency), approved variation values (currency), payments already received (currency), incremental labour cost of variations (currency), incremental material cost of variations (currency). Keep amounts in the units shown on each field. The example is a starting point, not a recommended value.
| Input | Example value |
|---|---|
| Original contract sum (currency) | 10000 |
| Approved variation values (currency) | 1000,-500 |
| Payments already received (currency) | 6000 |
| Incremental labour cost of variations (currency) | 200 |
| Incremental material cost of variations (currency) | 100 |
A worked example
With the example inputs above, net approved contract variation (currency) is 500. Change the inputs to explore your own scenario.
| Result | Example answer |
|---|---|
| Net approved contract variation (currency) | 500 |
| Revised contract total (currency) | 10,500 |
| Remaining contract balance (currency) | 4,500 |
| Variation contribution change (currency) | 200 |
How this is calculated
Net approved contract variation (currency)
Add increases and deduct approved credits.
Revised contract total (currency)
Apply net approved variations to original contract.
Remaining contract balance (currency)
Deduct received payments from revised contract value.
Variation contribution change (currency)
Deduct incremental labour and materials from variation revenue.
Symbols and units
- a
- Original contract sum (currency)
- b
- Approved variation values (currency)
- c
- Payments already received (currency)
- d
- Incremental labour cost of variations (currency)
- e
- Incremental material cost of variations (currency)
Use the units shown. A list keeps the order in which you enter its values. The symbol ^ means “raised to the power of”.
Assumptions and limits
Signed variations are already approved; balances do not establish the due date or payment entitlement.
Calculations use the values you enter. Blank or invalid inputs show an error instead of silently substituting zero. Results are displayed to useful precision; calculations retain the underlying numeric precision.
Questions about this tool
What does the result tell me?
Net approved contract variation (currency); Revised contract total (currency); Remaining contract balance (currency); Variation contribution change (currency). The result applies to the method and inputs described above. Check the units and assumptions before using it in a decision.
Why might another calculator differ?
Differences in units, rounding, timing or model definitions can produce different answers. Compare the input definitions and the method, rather than only the final number. For this tool: Signed variations are already approved; balances do not establish the due date or payment entitlement.
Are my inputs stored or sent to AI?
Calculations on this page happen in your browser. The separate AI question finder sends its submitted conversation to OpenAI; these calculator fields are not sent. Favourites and recent tool names are stored locally. A shared link contains the inputs you choose to include.
Further reading
OpenStax: Describe and Identify Cost Drivers ↗
Background reading; this does not imply endorsement or independent review of SumFizz.
Review status
Software example and browser checks are recorded in our quality report. No external expert review is claimed. Created with coding assistance; calculations run as ordinary browser code.
Read the quality report →