The uncertainty of any estimated range is defined as the spread between the High and Low estimates, expressed as a percentage of the High estimate:
Uncertainty % = ((High - Low) / High) * 100If High is 0 or unestimated, uncertainty is 0%.
Because the formula divides by the High estimate, uncertainty is cleanly bounded between 0% and 100%. For example:
| Range (Low to High) | Spread (High - Low) | Uncertainty % | Meaning |
|---|---|---|---|
4d to 4d | 0d | 0% | Absolute certainty. No variance expected. |
3d to 4d | 1d | 25% | High confidence. Small, well-defined buffer. |
2d to 4d | 2d | 50% | Moderate uncertainty. Scope is understood, but implementation details vary. |
1d to 5d | 4d | 80% | High volatility. Significant unknowns or unvetted external dependencies. |
0d to 5d | 5d | 100% | Maximum uncertainty. Pure exploratory spike or completely unknown territory. |
When aggregating issues across a parent ticket, an epic, or an entire project, bounds are summed independently:
Total Low Estimate = Sum of all individual Low estimates
Total High Estimate = Sum of all individual High estimates (or Low estimate if High is unset)
Example Rollup:
1d to 3d2d to 4d1d to 1d(1+2+1)d to (3+4+1)d = 4d to 8d((8 - 4) / 8) * 100 = 50%Summing ranges in this manner preserves absolute best-case and worst-case boundaries, giving stakeholders a realistic risk range.