Understanding Heart Rate Training Zones
Training in the right heart rate zone is one of the most effective ways to structure your workout programme. Each zone targets a different energy system, delivering different physiological adaptations.
The Three Max HR Formulas
220 − Age (Fox Formula)
The most widely known formula. Simple and easy to use, though it has a standard deviation of ±10–12 bpm, meaning it can be significantly off for individuals who are very fit or unfit. Best for: quick estimates when you don't have lab data.
Tanaka Formula (208 − 0.7 × Age)
Published in 2001 after a meta-analysis of 351 studies with over 18,000 subjects. Shown to be more accurate than the 220-age formula, especially for adults over 40. The equation reflects that max HR decreases more slowly with age than the Fox formula suggests. Best for: adults over 40 who train regularly.
Karvonen Formula (Heart Rate Reserve)
The Karvonen formula accounts for your resting heart rate (RHR) by working with your heart rate reserve — the difference between your max HR and your RHR. The formula for a target intensity is: target = ((maxHR − restHR) × intensity%) + restHR.
This produces more personalised zones since a fit person with a low resting HR will have different zones from a sedentary person of the same age and max HR. Best for: athletes who know their resting HR and want the most personalised zones.
The 5-Zone Garmin Model
Garmin devices use a 5-zone model based on percentages of max HR. These match the zones this calculator produces and can be entered directly into the Garmin Connect app under User Settings → Heart Rate Zones. Each zone produces a different physiological response:
- Zone 1 (50–60%) — Recovery and warm-up. Burns mostly fat. Very easy conversation.
- Zone 2 (60–70%) — Aerobic base building. The "magic zone" for endurance development and fat burning.
- Zone 3 (70–80%) — Aerobic fitness. Moderate effort. Improves cardiovascular efficiency.
- Zone 4 (80–90%) — Lactate threshold. Very hard effort. Trains the body to clear lactic acid faster.
- Zone 5 (90–100%) — VO2max and max effort. Anaerobic. Short-duration, maximum intensity intervals.
How to Find Your True Max HR
Formulas are estimates. The most accurate way to find your max HR is to measure it directly. Options include a VO2max test in a lab, a graded exercise test on a treadmill, or a hard racing effort with a heart rate monitor. Once you have a measured value, use the "I know my max HR" option above for the most accurate zones.
Zone 2 Training — Why It Matters
Elite endurance athletes spend 75–80% of their training volume in zone 2. At this intensity, the body adapts by increasing mitochondrial density, improving fat oxidation, and building capillary networks in the muscles. The result is a higher aerobic ceiling — you can go faster at the same heart rate.
If you're new to structured training, a simple starting plan is: 3 zone 2 sessions per week of 45–60 minutes, plus 1 session with zone 4 intervals. Resist the urge to push into zone 3 — it's the "grey zone" that's too hard for recovery and too easy for adaptation.
How to Use This Calculator
Select your preferred formula — Tanaka for most adults over 30 who train regularly, Fox (220 − age) for quick estimates, or Karvonen if you know your resting heart rate and want personalised zones. If you have measured your max HR in a lab or hard race effort, enter it directly. For the Karvonen method, measure your resting heart rate first thing in the morning lying in bed, averaged over 5 consecutive days. The zones display as bpm ranges you can enter directly into your GPS watch, Garmin Connect, or training platform.
Common Heart Rate Zone Mistakes
The most common error is training in zone 3 while believing it is productive zone 2. Zone 3 ('comfortably hard') feels like quality training but produces neither the aerobic base development of true zone 2 nor the high-intensity stimulus of zone 4 — endurance coaches call it the 'grey zone.' The fix: be strict with pace. If your heart rate creeps above your zone 2 ceiling on a run, slow down regardless of how easy it feels. This is especially important in heat, after illness, or during high training load weeks when cardiac drift is more pronounced.
A second common mistake is using the Fox formula (220 − age) without recognising its wide individual variation. The formula has a standard deviation of ±10–12 bpm — your actual max HR could be 24 bpm higher or lower than predicted. If your training zones feel consistently too hard or too easy, your max HR estimate is likely off. Use the Tanaka formula as an alternative, or better yet, measure your max HR directly in a lab or at the end of a maximal interval session.
HR Zones for Wheelchair Athletes and Adaptive Sport
Heart rate zone calculations apply identically to wheelchair athletes — the same formulas work. However, arm-based exercise (handcycling, wheelchair basketball, seated rowing) typically generates a lower max heart rate than leg-based exercise in the same individual, often by 5–10 bpm. If you compete in both arm-powered and leg-powered sports, your HR zones may differ slightly by discipline. Measure your max HR specifically for each context if you train in both. Resting heart rate — used in the Karvonen formula — is the same regardless of discipline.
Frequently Asked Questions
Should I train by heart rate or by power?
For running, heart rate is the most practical metric since power meters are still relatively uncommon outside elite competition. For cycling, power is generally preferred — it is instantaneous and unaffected by heat, fatigue, or caffeine, all of which raise heart rate without changing actual output. The best approach combines both: power for interval prescription and execution, heart rate for recovery monitoring and zone 2 runs. On easy days, if your heart rate is higher than expected at the same pace or power, your recovery is incomplete.
How often should I recalculate my heart rate zones?
Recalculate every 8–12 weeks during a consistent training phase, or after any significant fitness change: returning from injury, completing a race block, or finishing a base-building phase. As cardiovascular fitness improves, resting heart rate typically decreases, which shifts Karvonen zones upward (larger heart rate reserve). Fixed-max-HR methods (Fox, Tanaka) only need updating if evidence suggests your max HR has changed — uncommon, but possible with significant age progression, illness, or medication changes.