Interval Pace Calculator
Interval session arithmetic — the pace for each rep, the rest between them, and how long the whole session takes.
Interval pace is normally set as a percentage of race pace or from a recent time trial.
How the interval pace calculator works
Interval pace is normally set as a percentage of race pace or from a recent time trial. The part people get wrong is the total: eight 800s does not take eight times the rep time, because the recoveries add up to as much again.
The work-to-rest ratio is what defines the session. One-to-one develops VO₂ max; one-to-half is a threshold session in disguise; two-to-one is closer to a tempo run with breaks.
Formula: session = reps × (rep time + rest); pace = rep time / distance
Worked examples
| Inputs | Total session time | Note |
|---|---|---|
| 8 × 800 m in 2:45 | 1:01:00 | about 62 minutes total |
| Shorter recoveries | 54:00 | a much harder session |
| Fewer reps | 46:45 | under 45 minutes |
FAQFrequently asked questions
How long should interval recoveries be?
It depends what you are training. Equal work and rest develops VO₂ max; shorter recoveries push it toward threshold; longer ones toward speed.
Why is my session longer than I expected?
Because the recoveries add up. Eight 800s with two-minute rests spend fourteen minutes standing still, plus the warm-up.
What pace should intervals be?
For VO₂ max work, roughly 3 to 5 km race pace. Running them faster trains a different system and costs more recovery.
Should I jog or stand during recovery?
Jogging clears lactate faster and keeps the aerobic system engaged. Standing suits genuinely maximal short reps.
How many intervals is enough?
Enough that the last rep is as fast as the first, and no more. A session where the pace falls away has stopped training what it was meant to.
Where these figures come from
- Riegel PS, "Athletic records and human endurance", American Scientist 1981 — T2 = T1 × (D2 ÷ D1)^1.06
- Cooper KH, "A means of assessing maximal oxygen intake", JAMA 1968 — the 12-minute run test
- Ainsworth BE et al., Compendium of Physical Activities (2024 update) — MET values by activity
- OpenPowerlifting — DOTS coefficients (Tim Konertz, 2019) — the DOTS polynomial used for scoring
- Naismith's rule (1892) as used by UK and Australian walking bodies — 1 hour per 5 km plus 1 hour per 600 m of ascent
- UK Sport — national high-performance body
Last checked: September 2026. Formulas are fixed by their published sources; the MET values come from the Compendium of Physical Activities.