Two Sheets, One Consistent Logic
Sheet 1 – Hourly Rate per Role. From gross salary including employer National Insurance contributions and statutory pension contributions to total employer labour costs, divided by productive hours, complemented by overhead surcharges and profit margin markups.
Sheet 2 – Effort Estimation per Work Package. Planned hours per role, valued at the internal billing rate, supplemented by a dedicated risk buffer per work package, external contractor costs, and travel expenses — leading all the way to the final quote price and the expected contribution margin.
The Pitfall This Template Prevents
The "Productive Hours" column is deliberately separated from contractual working hours. Dividing total labour costs by contractual annual hours instead typically underestimates the true cost rate by 25 to 35 percent.
| Divisor | Sample Rate |
|---|---|
| 2,080 contractual hours | £43.70 |
| 1,656 attendance hours | £54.88 |
| 1,325 productive hours | £68.60 |
The variance is 57 percent. Only the final figure is viable for project cost calculation.
Calculating Productive Hours
The calculation baseline is the contractual annual working time, minus statutory public and bank holidays, statutory annual leave entitlement (under the Working Time Regulations 1998), empirical allowances for sick leave (under Statutory Sick Pay benchmarks), and professional development. What remains are actual attendance hours. From this figure, deduct the proportion allocated to non-billable internal duties — which varies significantly by role:
| Role | Share of Billable Project Work |
|---|---|
| Project Team Member | 75–85% |
| Project Manager | 55–70% |
| Technical Lead / Practice Lead with Business Development Share | 40–55% |
The Risk Buffer
Risk buffers are purposefully allocated per individual work package rather than applied as a blanket markup on the overall total. The rationale: estimation uncertainty varies significantly across packages. A well-defined, standardised work package may only require a 5 percent buffer, whereas an exploratory task might require 30 percent.
Applying a blanket markup of 10 percent across the board provides a less accurate approximation — and is much harder to justify during client negotiations.
Feedback Loop via Post-Project Costing (Variance Analysis)
Initial project calculation is an estimate based on assumptions. Only direct comparison with actual tracked working time reveals whether those assumptions held true.
Two key metrics should be reviewed annually:
- Productive Hours — Were target billable hours achieved, or was the original assumption overly optimistic?
- Overhead Surcharge — Did allocated overhead cost surcharges cover actual indirect expenses?
Both metrics can only be determined accurately if all working hours performed are tracked comprehensively — including fixed-price projects, where time tracking is most frequently neglected.