Understanding Cost Overrun Percentage
How we calculate. Overrun % = (actual − budget) ÷ budget × 100 (negative = under budget). See our methodology and accuracy policy .
Real-world scenario: A typical Cost Overrun Percentage case uses actual cost 11200000 and budget 10000000. Enter the same figures below to reproduce the worked path.
What is Cost Overrun Percentage?
A simple budget variance KPI. Distinct from CPI/CV on the Professional hub, which use earned-value formulas.
- Same cost basis (committed vs incurred)
- Positive = over budget
- Cross-link CPI for EV cost performance
The Formula
Worked Example
Common Use Cases
- Cost reports: budget burn
- Forecast reviews: overrun risk
- Package compare: trade overruns
Pro Tips
- Freeze the budget baseline
- Separate approved COs from true overrun
- Use CPI for EV analytics
| Scenario | When to use |
|---|---|
| Percent of a number | Finding a part of a whole (tax, tip, score) |
| Percent change | Comparing old vs new values |
Limitations: Cost Overrun Percentage results are educational construction planning aids—not engineering, safety, legal, or cost-estimating advice. Confirm definitions with your project controls, safety, and contract documents. For earned-value SPI/CPI see the Professional hub.
Common mistakes
- Swapping part and whole: The denominator must be the full total, not a subset.
- Rounding too early: Carry extra decimal places through multi-step work before rounding the final percent.
- Mixing percent and decimal forms: Enter rates in the format the calculator labels expect.
When to use this calculator
- Use this page when your wording matches cost overrun percentage and the form labels on screen.
- Use percent of a number for “what is X% of Y?” problems.
- Use number is what percent when you know part and whole and need the percent.
Still unsure about cost overrun percentage? Start with the quick answer above, then open the linked calculator that matches your wording.
❓ Frequently Asked Questions
How do I use this cost overrun percentage calculator?
For cost overrun percentage (percentage calculator), enter the values labeled on the form, then press Calculate. Compare the result to the worked example on this page.
What formula does this page use?
See the quick answer and formula box above for cost overrun percentage—the same percentage calculator expression is applied to your inputs.
What if my result looks wrong?
When checking cost overrun percentage, re-check part vs whole (or rate vs base), rounding, and whether percents were entered as 25 rather than 0.25 when the form expects percents.
Authoritative References
For construction project controls and safety rate concepts, consult: