Estimate how much scoped project work fits into a realistic week after admin time and a deliberate schedule reserve. The calculator converts working hours into usable billable hours, weekly capacity, monthly capacity, and protected buffer time so commitments are based on delivery time rather than an idealized calendar.
The main result is sustainable weekly throughput before rounding. Monthly capacity is an average for planning, not a promise for every calendar month.
Capacity is a planning estimate. Holidays, deadlines, client response time, and task dependencies can reduce actual throughput.
With 40 weekly hours, 30% nonbillable time, a 15% reserve, and 12 hours per scope unit, usable time is 23.8 hours. Capacity is 1.98 units per week, or about 8.6 per month, with 4.2 hours protected weekly.
Admin, selling, invoicing, and meetings consume time but do not complete scoped project work; excluding them prevents overbooking.
Round down for firm commitments. Treat fractional capacity as flexibility, not a guaranteed extra delivery.
Use it for coordination, handoffs, and scope clarification, illness, and normal estimation error.
Yes. The calculator uses 52 ÷ 12, about 4.33 weeks per average month.
Decimal hours are accepted, but include all direct preparation and delivery time in the estimate.
| Variable | Meaning | Unit |
|---|---|---|
| Weekly working time | All available work time | hours/week |
| Nonbillable share | Time unavailable for delivery | % |
| Schedule reserve | Protected portion of remaining time | % |
| Hours per unit | Direct effort for one unit | hours |