COCOMO Effort Estimation Surface

Project Parameters

Project size 120 KLOC

Development mode

Effort Adjustment Factor 1.00

Estimate

Effort E

— PM

Schedule D

— mo

Average team size

— people

Semi-detached: coefficients a=3.0, b=1.12 — a mixed-experience team on a moderately novel system.

How it works

The COCOMO (Constructive Cost Model, Boehm 1981) estimates software effort from a single size measure — thousands of lines of code (KLOC) — plus a mode that captures how novel and constrained the project is:

Effort E = a × (KLOC)^b × EAF   [person-months]
Duration D = c × E^d           [months]
Team size  = E / D             [average people]

Organic:        a=2.4  b=1.05  c=2.5  d=0.38
Semi-detached:  a=3.0  b=1.12  c=2.5  d=0.35
Embedded:       a=3.6  b=1.20  c=2.5  d=0.32

The exponent b > 1 is the key insight: effort grows faster than code size, because a bigger system needs proportionally more integration, coordination and communication overhead — doubling KLOC more than doubles the effort. The Effort Adjustment Factor (EAF) is the Intermediate-COCOMO multiplier applied on top, aggregating cost drivers like required reliability, team capability and tooling (typically 0.7 for a very favorable project down to 1.4 for a difficult one).

Project size slider — moves the KLOC axis; the surface itself doesn't change, only where you sit on it.
Development mode — swaps (a, b, c, d) and redraws the whole surface, since the exponent itself changes.
EAF slider — scales effort directly; the marker rises or falls along the depth axis without moving in KLOC.

The grid is a real height field: each cell's color and height is E = a·KLOC^b·EAF for that cell's own (KLOC, EAF) pair, log-scaled for legibility — the bright marker sphere is your current parameter choice plotted on that same surface.

Current estimate Effort surface (KLOC × EAF)

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