A single test — 30 minutes all-out — gives you up to three sets of zones: by pace, by heart rate and, if you run with a meter, by power. Enter whatever you measured.
Each sport uses a different test and a different metric. Pick one and we'll walk you through it.
More than one test is valid and they all get you to the same place. Pick the one you did — the maths changes depending on which.
If you have more than one metric, trust them in this order: power > pace > heart rate. HR lags behind the effort and drifts with heat, sleep and caffeine — it's the backup, not the main signal.
Having the numbers is half of it. The other half is knowing which session grows each zone — how to build a Z2 that's more than easy miles, the marathon-pace session that justifies Zone X, and what a real threshold set looks like. We'll email you the full guide.
The full PDF guide: the sessions for every zone, for swimming, cycling and running. One email, nothing else, and you can unsubscribe whenever you want.
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The same ones I use with my athletes, built on this zone structure.
Running plans are organised by race distance rather than by zone — pick your distance in the running plans, and the zones you just calculated are already built into them.
Run 30 minutes all-out, as evenly as you can hold it. Three numbers come out of it: average pace over the 30 minutes is your threshold pace, average heart rate over the last 20 minutes is your LTHR, and — if you run with a power meter — average power over the 30 minutes is your threshold power.
Early, rested, fed and hydrated. A flat uninterrupted loop: no traffic lights, no crossings, because every stop invalidates the average. Chest strap, always. If you do have to stop, the test isn't rescued by estimating — it can be recovered by calculating over the last 10 clean minutes, or repeated the following weekend with the cause fixed.
If you have more than one, the order is power > pace > heart rate. Power measures the work directly. Pace is excellent on the flat and a liar uphill, into wind, or on trail. Heart rate reacts late and drifts with heat, sleep and caffeine.
That's about which one to believe when they disagree, not about which to use: the calculator shows you every metric you measured, because in practice you'll look at one or the other depending on the day and the terrain.
If you run with a power meter, these are power zones for the seven-zone 80/20 model — not the zones your meter's own software ships with, which usually uses five and splits them differently. The numbers are not interchangeable: use these with this model and the sessions in your plan will land where they're meant to.
Look at Zone X once you have the table. It's the top half of Zone 2, near enough your marathon pace, and it's separated on purpose: it accumulates a lot more fatigue than low Z2 without giving much more aerobic benefit in return.
It's where most people overtrain without noticing. You head out easy, you feel good, the pace settles a few seconds quicker on its own, and you end up spending three sessions a week there. It feels like training. You arrive at your quality day with nothing in your legs.