How to use Heart Rate Zone Calculator
The heart rate zones calculator computes your five training zones from your maximum heart rate (MHR) or using the Karvonen method which also accounts for resting heart rate. Zone 1 (50–60% MHR) is recovery; Zone 2 (60–70%) burns fat and builds aerobic base; Zone 3 (70–80%) improves cardiovascular efficiency; Zone 4 (80–90%) boosts lactate threshold; Zone 5 (90–100%) builds peak power. Knowing your zones prevents overtraining and under-training.
- Choose Simple (% of MHR) or Karvonen method(requires resting heart rate).
- Enter your age — MHR is auto-estimated as 220 − age.
- Optionally override MHR with a measured value from a recent maximal-effort test.
- For Karvonen, enter your resting heart rate (measure first thing in the morning).
- Review your five zones with bpm ranges, purpose and recommended session duration.
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Simple % MHR vs Karvonen formula
The simple method sets zones as fixed percentages of MHR: accurate enough for most recreational athletes. The Karvonen (heart rate reserve) method factors in resting heart rate: Target HR = Resting HR + (HRR × intensity%). Since a lower resting HR means a higher heart rate reserve, the Karvonen formula gives higher absolute zone values for fit athletes — more accurately reflecting true physiological effort.
Training effect of each zone
Zone 2 training (fat-burn) is the foundation of aerobic fitness — elite endurance athletes spend 70–80% of training volume here. Zone 3 stimulates mitochondrial density improvements. Zone 4 raises the lactate threshold, the primary determinant of race pace. Zone 5 sessions are short and high-stress; over-relying on them without Zone 2 base leads to overtraining. The optimal training mix depends on your sport and fitness phase.
| Zone | Name | % MHR | Primary benefit | Typical session |
|---|---|---|---|---|
| 1 | Recovery | 50–60% | Active recovery, blood flow | Easy walk or spin, 30–60 min |
| 2 | Fat Burn | 60–70% | Aerobic base, fat oxidation | Long slow runs, 45–90 min |
| 3 | Cardio | 70–80% | Cardiovascular efficiency | Steady-state effort, 20–45 min |
| 4 | Threshold | 80–90% | Lactate threshold | Tempo runs, 10–30 min |
| 5 | Anaerobic | 90–100% | Peak power output | Intervals, 2–10 min |
Worked examples
Zone 2 for a 40-year-old
Inputs: Max HR = 220 − 40 = 180 bpm
Result: Zone 2 (60–70%) ≈ 108–126 bpm
Karvonen zone 2
Inputs: Age 30, resting 60 (max 190, HRR 130), 70%
Result: 60 + 0.70×130 = 151 bpm
Heart-rate zones for a 40-year-old (max ≈ 180 bpm)
| Zone | % of max | Target bpm |
|---|---|---|
| Zone 1 (recovery) | 50–60% | 90–108 bpm |
| Zone 2 (fat burn) | 60–70% | 108–126 bpm |
| Zone 3 (cardio) | 70–80% | 126–144 bpm |
| Zone 4 (threshold) | 80–90% | 144–162 bpm |
| Zone 5 (anaerobic) | 90–100% | 162–180 bpm |
Glossary
- MHR
- Maximum Heart Rate — the highest heart rate achievable during maximal effort exercise.
- HRR
- Heart Rate Reserve — the difference between MHR and resting heart rate.
- Karvonen
- A heart rate zone formula that uses HRR to set more personalised training targets.
- Lactate threshold
- The exercise intensity at which blood lactate begins accumulating faster than it can be cleared.
Related reading
Frequently Asked Questions
Why use Heart Rate Zone Calculator?
- Calculates all five training zones using simple % MHR or the Karvonen heart-rate-reserve method
- Supports measured MHR override for athletes with a verified maximal-effort test result
- Displays each zone's purpose and recommended session duration alongside the bpm range
- Karvonen method produces personalised zone values that reflect true fitness-adjusted effort
Common use cases
- Set target bpm ranges on a GPS watch or chest strap before a structured training session
- Plan a Zone 2 aerobic base block by identifying the bpm ceiling to stay below during long runs
- Verify whether a recent run reached Zone 4 threshold territory based on recorded heart rate data
- Compare simple-MHR and Karvonen zones to understand how resting heart rate shifts your targets
- Schedule Zone 5 interval sessions within a weekly training plan without exceeding recovery capacity
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