Training Pace Calculator

What this generator does

Derives a target pace for each training effort from the 5k pace you enter, then applies it to a set of repeats so you get a split time per repeat rather than a pace per kilometre. The catalogue already has an interval session generator that builds run/rest blocks; this answers the different question of what speed those blocks should actually be run at.

How to use this tool

1. Enter your current 5k race pace per kilometre — the pace you could race today, not your goal.
2. Pick an effort zone and the repeat distance you are planning.
3. Read the target split for each repeat.
4. Change the shape to see how a ladder or pyramid changes the numbers.

Understanding the controls

5k pace

Your current race pace, entered as minutes and seconds per kilometre. Using a goal pace instead of a current one is the usual way these calculations go wrong.

Effort zone

Easy through to repetition. Interval pace is 5k race pace by definition; everything else is derived from it.

Shape and repeat distance

Straight repeats all the same, or a ladder, pyramid or descending set. The split is recomputed for each distance.

Recovery

Expressed as a percentage of the repeat's own time, so recovery scales with the effort rather than being a fixed number that is too long for short reps and too short for long ones.

Common use cases

• Turning a vague "run these at threshold" into a number you can hit on a watch
• Checking whether an easy run is actually easy enough
• Working out 400 m or 800 m splits without doing the arithmetic on a track
• Comparing what the same session costs at two different fitness levels
• Planning a session before a track night rather than improvising it

How this generator works

Each zone has a multiplier against 5k race pace — easy is 1.35 times slower, threshold 1.07, repetition 0.93. The target pace is your 5k pace times that multiplier, and each repeat's split is that pace scaled to the repeat distance. Every split shown is recomputed from its own distance rather than carried forward, and the session totals are re-added before display.

Randomness and fairness

The pace arithmetic is entirely deterministic — the same 5k pace always gives the same targets. The only random element is which coaching cue appears alongside the session; a seeded draw fixes that and is reproducible and therefore explicitly not cryptographically secure, while an unseeded one uses the browser's cryptographically secure generator.

For how randomness is produced across the whole site, see how Generate Random works.

Limitations and good to know

• The zone multipliers are a widely used training convention, not a measurement of your physiology. Treat them as a starting point and adjust by feel.
• It assumes your entered 5k pace is current. Using a goal pace produces targets you cannot hold, which is the fastest way to ruin a session.
• Terrain, heat, wind and altitude all change what a given pace costs, and none of them are modelled.
• Hitting these paces does not by itself produce any particular result — training outcome depends on far more than one session.
• Nothing is stored between visits, so note down anything you want to repeat next week.

Privacy and your data

Your pace and session settings are used only to do arithmetic in your browser. No times, distances or generated sessions are transmitted or kept between visits.