Software Team Size Calculator
Find the average team size an effort and schedule imply.
What this calculator does
Effort divided by schedule, exactly as the published model relates the two. No staffing curve or ramp-up profile is assumed.
Inputs and what they mean
- Estimated effort
- — Person-months from your sizing model..
- Planned schedule
- — Calendar months the work has..
How to use it
- Enter your own figures — the calculator never fills in a rate, price or benchmark for you.
- Press Calculate to see the result.
- Read the formula, variables, assumptions and source below the result before you rely on it.
Formula
Average staff = Effort in person-months ÷ Schedule in calendar months
Worked example
286 person-months over 22 months
The published staffing relation: average staff is effort divided by schedule.
Reading the result
The headline figure is the main answer. Any breakdown underneath shows the parts that make it up, so you can check the working and see what changes when you adjust an input.
Limitations and assumptions
Results depend entirely on the figures you enter and are rounded for display. They are for general information and education, not professional advice.
Reference: University of Southern California, Center for Systems and Software Engineering — COCOMO II model definition manual
Last reviewed:
Common questions
Formula, source and verification
The published staffing relation between effort and schedule.
The question it answers: How many people do we need on average to finish in the time we have?
The formula
Average staff = Effort in person-months ÷ Schedule in calendar months
- PM — Estimated effort
- (person-months). Effort from the organisation's sizing model.
- TDEV — Planned schedule
- (months). Calendar months the work has.
Units: Person-months; months; people.
What kind of calculation this is
Deterministic formula. The same inputs always give the same answer. The maths is fixed and does not depend on judgement.
Method
Effort divided by schedule, exactly as the published model relates the two. No staffing curve or ramp-up profile is assumed.
Assumptions built into the result
- Mathematical: Staffing is treated as an average across the schedule, not as a ramp.
Figures this calculator will never guess for you
- No industry delivery rate, productivity figure, defect rate or cost per line is inserted.
- No optional component is filled in on the user's behalf.
Limitations
- An average; real projects staff up and down over time.
- Says nothing about whether that team size is feasible.
Source and version
- Standard or reference
- COCOMO II post-architecture model — University of Southern California, Center for Systems and Software Engineering (COCOMO II Model Definition Manual — post-architecture effort PM = A × Size^E × ΠEM with A = 2.94 and E = B + 0.01 × ΣSF (B = 0.91), and schedule TDEV = C × PM^(D + 0.2 × (E − B)) × SCED%/100 with C = 3.67 and D = 0.28.)
- Published source
- University of Southern California, Center for Systems and Software Engineering — COCOMO II.2000
- Formula version
- Version 1
- Verification
- Reviewed against the cited source on
- How much weight the source carries
- Academic
- Applies to
- Currency
- The result is a ratio or index, so it does not depend on currency.
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