Quick guide
How to use this calculator
- Enter measurements from one real session, race, test or equipment setup.
- Keep distances, timing methods, course conditions and equipment conventions consistent.
- Use the component results to audit the arithmetic and retain the stated limitation.
Calculation method
Calculation method
Session density = active time ÷ (active time + rest time); active pace uses active time only.
Results describe only the entered record or scenario. They do not establish fitness, readiness, injury risk, medical safety, selection, qualification or an appropriate training plan.
Worked example
Worked example
A 45-minute active swim plus 15 minutes rest has 75% active-time density.
Session density = active time ÷ (active time + rest time); active pace uses active time only.
Supported inputs
Precision and limits
Measurement basis
Compare like with like: the same course, pool, equipment, timing convention or testing protocol where that distinction affects meaning.
No prescription
Heart-rate percentages, external load, activity intensity and workload are entered arithmetic. This page does not prescribe training or determine whether exercise is medically appropriate.
Privacy and precision
Values remain in this browser. Invalid, contradictory and non-finite states return explicit errors.
Calculator-specific boundary
This is entered-performance arithmetic, not training, medical, injury-risk, selection or fitness-for-duty advice.
Continue calculating