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Change Order Impact Calculator

Work out change order impact instantly with clear inputs, formula shown and shareable results.

About Change Order Impact Calculator

A change order carries both a direct cost and a time impact, and the time impact brings prolongation cost — site overheads, supervision and plant standing time — which is often claimed separately. Estimating it at around 15% of the pro-rata contract value for the extension period gives an early exposure indication.

Formulas

Revised value

Revised = Original contract value + Change order value

Implied prolongation

Prolongation = Original value / Duration x Extension weeks x 15%

Worked example

With the default values below, Change Order Impact Calculator returns Revised contract value of $28,100,000.00. Change any input above and every figure here is recalculated in your browser.

Inputs used

Original contract value
26,000,000
Change order value
2,100,000
Original duration
52
Time extension claimed
5

Results

Revised contract value
$28,100,000.00
Growth in contract value
8.077%
Growth in duration
9.615%
Implied prolongation cost exposure
$375,000.00

Step by step

  1. 1Values used
  2. 2Revised value
  3. 3Implied prolongation
  4. 4Revised contract value= 28,100,000.00
  5. 5Growth in contract value= 8.077
  6. 6Growth in duration= 9.615
  7. 7Implied prolongation cost exposure= 375,000.00

Assumptions and limits

  • The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
  • In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
  • Figures are rounded for display to 3 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
  • Indicative estimate only. Fees, entitlements, limits and formulas vary by jurisdiction, statute, policy wording and the facts of the case. This is not legal, tax, insurance or financial advice — confirm with a qualified professional or the relevant authority.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Indicative estimate only. Fees, entitlements, limits and formulas vary by jurisdiction, statute, policy wording and the facts of the case. This is not legal, tax, insurance or financial advice — confirm with a qualified professional or the relevant authority.

Frequently Asked Questions

Should time and cost be agreed together?

Yes, always. Agreeing cost while leaving the time impact open is the single most common route to a later prolongation claim.

When does cumulative change become a problem?

Beyond about 15-20% of original value the contract has effectively changed in character, which can raise procurement compliance questions.

Related Calculators

Change Order Impact Calculator | Calcrivo