Heart Rate Zones Calculator
Calculate your five training heart rate zones based on age or max heart rate.
Optimize cardio, fat burn, and endurance training.
How Heart Rate Training Zones Work
Heart rate zones are percentage ranges of your maximum heart rate (MHR). Training at different intensities produces different physiological adaptations — from fat burning at low intensities to speed and VO2max development at high intensities.
Maximum heart rate estimation:
The most widely used formula (Tanaka, 2001):
MHR = 208 − (0.7 × Age)
The older Fox formula (220 − Age) is less accurate for older athletes. The Tanaka formula is preferred.
Worked example: 38-year-old runner:
MHR = 208 − (0.7 × 38) = 208 − 26.6 = 181 bpm
The 5 training zones:
| Zone | % of MHR | bpm (181 MHR) | Purpose |
|---|---|---|---|
| Zone 1 | 50–60% | 91–109 | Recovery, easy walking |
| Zone 2 | 60–70% | 109–127 | Fat burning, aerobic base |
| Zone 3 | 70–80% | 127–145 | Aerobic conditioning |
| Zone 4 | 80–90% | 145–163 | Lactate threshold, race pace |
| Zone 5 | 90–100% | 163–181 | VO2max, maximum effort |
Key training principles:
- Zone 2 is where most training volume should occur (60–80% of weekly mileage), it builds aerobic capacity with minimal injury risk
- Zone 4 is where 10K and half-marathon race pace typically falls
- Zone 5 intervals (30 sec to 4 min) are used sparingly to increase maximum oxygen uptake
Heart rate reserve method (Karvonen: more precise):
Target HR = ((MHR − Resting HR) × Zone%) + Resting HR
For a person with resting HR of 55 bpm targeting Zone 3 at 70%:
Target HR = ((181 − 55) × 0.70) + 55 = 88.2 + 55 = 143 bpm
Use a chest strap monitor for accuracy. Wrist optical sensors can lag by 10–15 seconds during interval training.
Finding your true max heart rate
The Tanaka formula is an estimate; individual MHR can vary ±10–15 bpm from the predicted value. To find your actual max:
- Field test (running): After a 15-minute warm-up, run 3 × 800 m all-out with 90 seconds of recovery between each. Record the highest HR seen. The third interval usually produces it.
- Field test (cycling): 20-minute warm-up, then 5 minutes building to all-out effort on a steady climb. Hold the maximum sustainable HR for the last minute.
- Lab test: A VO2max test in an exercise physiology lab gives the most accurate MHR plus your ventilatory thresholds.
Re-test once a year. Max HR drops about 0.7 bpm per year of age, in line with the Tanaka formula.
Long-course endurance pacing
For triathlon and marathon distance racing, most volume sits in Zones 1–2 (the aerobic base). Race-day pacing per discipline:
- Ironman bike: 70–80% of max HR (Zone 2 to low Zone 3)
- Ironman run: 75–80% of max HR
- Marathon race pace: ~80–85% of max HR (Zone 4)
- Half-marathon race pace: 85–90% of max HR (Zone 4 to low Zone 5)
Going above Zone 3 on the Ironman bike almost always results in a painful run; the legs feel destroyed by mile 10 even if the cardiovascular system feels fine.
How we build and check this calculator
This calculator runs entirely in your browser, so the numbers you enter stay on your device. The math behind it is written by hand and tested against worked examples and standard references before the page goes live.
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