Function Point Effort Calculator
Turn a function point count into effort using your own delivery rate.
What this calculator does
Size × delivery rate, the standard function point estimating step. The delivery rate must be the organisation's own; no published or average rate is offered.
Inputs and what they mean
- Function points to build
- — number value.
- Your own hours per function point
- — Taken from your own completed projects. No industry rate is supplied..
- Hours in one person-month
- — number value.
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
Effort hours = Function points × Your hours per function point; Person-months = Effort hours ÷ Hours per person-month
Worked example
480 function points at your own 13 hours per point
The delivery rate comes from your own history, so the estimate stays yours.
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: International Function Point Users Group — Function Point Counting Practices
Last reviewed:
Common questions
Formula, source and verification
Functional size is multiplied by the organisation's own measured delivery rate.
The question it answers: How much effort will this take, given how fast we actually deliver?
The formula
Effort hours = Function points × Your hours per function point; Person-months = Effort hours ÷ Hours per person-month
- FP — Function points to build
- (FP). Unadjusted function points counted for the planned software.
- r — Hours per function point
- (h/FP). The organisation's own delivery rate, from its completed projects.
- h_m — Hours in one person-month
- (h). The hours the organisation counts as one person-month.
Units: Function points; hours per function point; hours.
What kind of calculation this is
Estimation model. This is a published estimation model. It produces an estimate, not a measured fact, and its accuracy depends on how well your situation matches the model.
Method
Size × delivery rate, the standard function point estimating step. The delivery rate must be the organisation's own; no published or average rate is offered.
Assumptions built into the result
- Mathematical: The delivery rate came from work comparable to the work being estimated.
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.
- No default hours-per-function-point value is provided.
Limitations
- An estimate, not a commitment; accuracy depends entirely on the delivery rate entered.
- Does not model schedule or team size.
Source and version
- Standard or reference
- Function point analysis — delivery rate measures — International Function Point Users Group (IFPUG, Function Point Counting Practices Manual — functional size is counted independently of technology, and delivery rate is effort per unit of functional size.)
- Published source
- International Function Point Users Group — CPM 4.3.1 family
- Formula version
- Version 1
- Verification
- Reviewed against the cited source on
- How much weight the source carries
- Standards or government
- Applies to
- Currency
- The result is a ratio or index, so it does not depend on currency.
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