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COCOMO Calculator (Software Effort & Schedule Estimate)

Estimate software development effort, schedule, team size and cost from KLOC with Boehm’s Basic or Intermediate COCOMO for organic, semi-detached and embedded projects.

Size (thousand lines of code, KLOC)

Project type

Model

Effort adjustment factor (EAF)

Cost per person-month

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How it works

Effort E = a × KLOCᵇ × EAF (person-months) · Time D = 2.5 × Eᵈ (months) · People = E ÷ D · Basic a/b/d: organic 2.4/1.05/0.38, semi-detached 3.0/1.12/0.35, embedded 3.6/1.20/0.32 · Intermediate a: 3.2, 3.0, 2.8 (EAF = product of 15 cost drivers)

COCOMO (Constructive Cost Model) was published by Barry Boehm in Software Engineering Economics (1981) from data on 63 projects. Effort grows slightly faster than size (exponent above 1) because larger systems need more coordination, and schedule grows much more slowly than effort, so big projects get bigger teams. Intermediate COCOMO multiplies the nominal effort by an effort adjustment factor built from 15 cost drivers such as reliability, complexity and team capability. Treat the result as an order-of-magnitude estimate; COCOMO II is the modern successor for current development practices.

Worked example

A 32 KLOC organic project with Basic COCOMO needs E = 2.4 × 32^1.05 = 91.3 person-months. The schedule is D = 2.5 × 91.3^0.38 = 13.9 months, so the average team is 91.3 ÷ 13.9 = 6.6 people, producing about 350 lines of code per person-month. At $8,000 per person-month the estimated cost is $730,649.

Sources: COCOMO — Basic and Intermediate model coefficients (Boehm, 1981) · COCOMO II online model (Ray Madachy)

Frequently asked questions

What is the COCOMO formula?

Effort = a × (KLOC)ᵇ person-months and development time = 2.5 × (Effort)ᵈ months, with a, b and d depending on the project type. For an organic project a = 2.4, b = 1.05 and d = 0.38.

What are organic, semi-detached and embedded projects?

Organic: small teams with experience in a familiar environment and relaxed requirements. Embedded: software tightly bound to hardware, regulation or real-time constraints. Semi-detached sits in between, with mixed experience and moderate constraints.

What is the effort adjustment factor?

In Intermediate COCOMO you rate 15 cost drivers (required reliability, database size, product complexity, analyst and programmer capability, tools, schedule pressure and others) from very low to extra high. Their multipliers are multiplied together into the EAF; 1.00 means all nominal.

Is COCOMO still used?

Basic COCOMO is mainly taught and used for quick sanity checks. COCOMO II (2000) adds scale factors and early-design models suited to modern iterative development, and is still used in cost estimating, particularly in defense and government.

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This calculator is for educational purposes. Double-check important results before acting on them.