Build a defensible time buffer for scoped project work by separating percentage uncertainty from known revision effort. The calculator shows buffered project hours, contingency time, its internal cost value, and the buffer’s share of the original estimate—useful when setting a delivery date or deciding what to include in a fixed fee.
Buffered hours combine the most likely effort with explicit contingency. The separate buffer value shows the revenue exposure if that contingency is omitted from pricing.
A buffer does not replace a clear scope, assumptions, acceptance criteria, or a change-control process.
For 30 base hours, a 20% uncertainty allowance, and 5 revision hours, the buffer is 11 hours and the buffered total is 41 hours. At $75 per hour, that contingency represents $825 of time.
A documented buffer covers identified uncertainty and review work; arbitrary padding has no stated basis.
This calculator applies uncertainty to base delivery effort only, then adds known revision hours separately.
No. It can remain an internal scheduling and pricing assumption while the client sees a clear total scope.
Yes, but a very high allowance usually signals that discovery or scope clarification should happen first.
Use the value of an hour you need to protect, often your target or effective billable rate, not necessarily the client-facing rate.
| Variable | Meaning | Unit |
|---|---|---|
| Base effort | Most likely delivery work | hours |
| Uncertainty allowance | Unknown work applied to base | % |
| Revision effort | Known review/change work | hours |
| Buffer value | Buffer hours × hourly value | USD |