How to use the training zones calculator
The page has two independent calculators. Use one or both.
Heart rate zones
- Enter your age and your resting heart rate (measure it in bed just after waking, or take the average from your watch over a week).
- If you know your real maximum heart rate from a hard test or race finish, enter it. Otherwise it is estimated from your age.
Training paces
- Pick a recent race distance: 5K, 10K or half marathon.
- Enter your finish time. You get your VDOT and five training paces per km and per mile.
The heart rate zones
Zones use the Karvonen (heart rate reserve) method: zone HR = resting HR + (max HR − resting HR) × intensity. It fits individuals better than a plain percentage of maximum heart rate because it accounts for fitness through your resting pulse.
| Zone | Intensity (% of HR reserve) | What it feels like | Used for |
|---|---|---|---|
| Z1 | 50–60% | Very easy | Recovery runs, warm-up |
| Z2 | 60–70% | Conversational | Most of your weekly mileage, long runs |
| Z3 | 70–80% | Comfortably hard | Steady and marathon-pace running |
| Z4 | 80–90% | Hard, short sentences | Threshold and tempo runs |
| Z5 | 90–100% | Very hard | Short intervals and hill repeats |
When no max is entered, it is estimated with the Tanaka formula (208 − 0.7 × age). This is only an average: real maximum heart rate can differ by 10 beats or more.
The training paces
Paces come from Jack Daniels’ VDOT system, the same method used in the race time predictor:
- E – Easy: most of your running, including long runs. Stay relaxed.
- M – Marathon pace: long steady blocks for marathon training.
- T – Threshold: about the pace you could hold for an hour. Run 20-minute tempo runs or 1–2 km repeats.
- I – Intervals: 3–5 minute repeats with equal recovery, to raise VO2 max.
- R – Repetitions: fast 200–400 m reps with full recovery, for speed and form.
For half marathon training, most runners get the biggest gains from plenty of E running plus one weekly T session.
Threshold pace calculator
Your threshold pace (T) is the effort you could hold for roughly an hour in a race. To find yours, enter a recent 5K, 10K or half marathon time in the training paces calculator: the T line is your threshold pace per km and per mile. Some examples, from a 10K time:
| 10K time | VDOT | Threshold pace |
|---|---|---|
| 40:00 | 51.9 | 4:07 /km (6:38 /mi) |
| 45:00 | 45.3 | 4:37 /km (7:25 /mi) |
| 50:00 | 40.0 | 5:05 /km (8:12 /mi) |
| 55:00 | 35.8 | 5:34 /km (8:58 /mi) |
Run one weekly session of 20 minutes at threshold pace or 3–4 × 6 minutes with 1 minute of jogging in between for half marathon fitness. In hot weather, hold the effort rather than the number.
Frequently asked questions
Heart rate or pace, which should I follow? Use pace on flat, cool days and heart rate on hot or hilly days, when the same pace costs much more effort. In summer in Spain, heart rate is often the more honest guide.
How often should I update my zones? Every 6–8 weeks, or after a new race result.
These estimates do not replace a lab test or medical advice. Check with a doctor before starting hard training.