Rex says
Everyday utility math — the kind you'd otherwise pull up four browser tabs for. I keep it to one clean answer.
Try a scenario
Click to load — tweak from there.Inputs
Result
Effective hourly
$102.56
Value of unbilled work
$2,400
Project margin
$3,710
Margin %
46.4%
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One click, a permanent link with your numbers baked in.
How to use this
- 1Enter quoted project fee ($).
- 2Enter planned hours.
- 3Enter unbilled extra hours.
- 4Enter your cost per hour ($).
- 5Read your effective hourly on the right — it updates as you type.
- 6Hit Share to keep the scenario or send it to someone.
About this calculator
Fixed-price projects die by a thousand small favours. Enter the quoted fee and the extra hours you absorbed to see the margin left standing.
Worked example
Using the values the calculator loads with:
Inputs
- Quoted project fee: 8000 $
- Planned hours: 60
- Unbilled extra hours: 18
- Your cost per hour: 55 $
Results
- Effective hourly: $102.56
- Value of unbilled work: $2,400
- Project margin: $3,710
- Margin %: 46.4%
What each field means
Inputs
- Quoted project fee ($)
- The quoted project fee used in the calculation, measured in $. Starts at 8000 $ so you have a working example on load.
- Planned hours
- The planned hours used in the calculation. Starts at 60 so you have a working example on load.
- Unbilled extra hours
- The unbilled extra hours used in the calculation. Starts at 18 so you have a working example on load.
- Your cost per hour ($)
- The your cost per hour used in the calculation, measured in $. Starts at 55 $ so you have a working example on load.
Results
- Effective hourly
- Returned as a money amount in US dollars and shown as the headline result. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- Value of unbilled work
- Returned as a money amount in US dollars. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- Project margin
- Returned as a money amount in US dollars. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- Margin %
- Returned as a percentage. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
FAQ
How does the scope creep cost calculator work?
Fixed-price projects die by a thousand small favours. Enter the quoted fee and the extra hours you absorbed to see the margin left standing. The underlying maths is: Effective rate = fee ÷ (planned + extra hours).
What do I need to enter?
4 values: quoted project fee, planned hours, unbilled extra hours, and your cost per hour. Each field starts with a sensible default, so you can change one number at a time and watch the result move.
What does the effective hourly result mean?
It is returned as a money amount in US dollars and updates live as you edit the inputs, so you can compare two or three versions of a scenario in a few seconds.
Is this calculator free, and do I need an account?
Yes, it's free, and no account is required. Nothing you type is stored on our servers — the maths runs entirely in your browser.
How accurate is the result?
It applies the standard formula exactly, so the arithmetic is precise. Estimates assume standard, average conditions — local rules, pricing, and materials vary.
Who is this tool for?
It's built for anyone doing everyday planning maths — a quick estimate that would otherwise need four browser tabs and a calculator app.
Accuracy and limitations
- Estimates assume standard, average conditions — local rules, pricing, and materials vary.
- Results are rounded for readability; add a buffer before ordering, booking, or committing.
- Double-check anything with a real cost attached against a local quote.
Related tools
Cite this calculator
Writing about this topic? Grab a citation — every link helps keep these tools free.
RevenueLab. (2026). Scope Creep Cost Calculator. Retrieved from https://www.revenuelab.fyi/toolbox/scope-creep-cost
<p>Source: <a href="https://www.revenuelab.fyi/toolbox/scope-creep-cost" target="_blank" rel="noopener">Scope Creep Cost Calculator — RevenueLab</a> (2026).</p>
Source: [Scope Creep Cost Calculator — RevenueLab](https://www.revenuelab.fyi/toolbox/scope-creep-cost) (2026).