Heart Rate Zone Calculator
Target zones for endurance, fat burning, threshold and VO₂max work.
Training Zones
| Zone | % Effort | BPM Range | Purpose |
|---|
Two Common Methods
% of Max HR is the simpler approach: Estimated Max HR = 220 − age. Tanaka et al. (2001) proposed the slightly more accurate 208 − 0.7 × age, which fits modern data better. Training zones are then a percentage of estimated MaxHR.
Karvonen (HR Reserve) incorporates your resting heart rate, producing zones that scale with cardiovascular fitness:
HRR = MaxHR − RestingHR
Target = RestingHR + (HRR × intensity%)
Karvonen is more accurate for trained athletes (lower resting HR = different relative zones). The Wikipedia article on heart rate covers both methods in detail.
The Five-Zone Model
| Zone | % MaxHR | Feels Like | Best For |
|---|---|---|---|
| 1 | 50-60% | Very easy, conversational | Recovery, warm-up, cool-down |
| 2 | 60-70% | Easy, nose-breathing possible | Endurance base, "fat burning" |
| 3 | 70-80% | Comfortable hard, can speak in short sentences | Aerobic / tempo |
| 4 | 80-90% | Hard, sustainable for 30-60 min | Threshold / lactate |
| 5 | 90-100% | Max effort, can hold only minutes | VO₂max intervals |
Why elite endurance athletes train mostly easy
Research by Stephen Seiler — published across multiple journals and summarized in a landmark 2010 review — found that elite endurance athletes across running, rowing, skiing, and cycling consistently train:
- ~80% of total time in Zone 1-2 (low intensity)
- ~20% in Zone 4-5 (threshold and VO₂max)
- Very little in Zone 3 ("medium hard")
This is counterintuitive — many recreational athletes do the opposite, spending most workouts in Zone 3 ("training plateau zone"). Too hard to recover from for the next workout, too easy to drive top-end adaptation. The 80/20 polarized model is now mainstream coaching wisdom across endurance sports.
Resting Heart Rate (RHR) as a Fitness Indicator
RHR is one of the cleanest measures of cardiovascular fitness. The American Heart Association reference ranges:
| RHR (bpm) | Fitness Level |
|---|---|
| 40-50 | Elite endurance athlete |
| 50-60 | Very fit |
| 60-70 | Above average |
| 70-80 | Average |
| 80-90 | Below average |
| 90+ | Possibly poor cardiovascular fitness — see a doctor |
Measure RHR first thing in the morning, before getting out of bed, for 60 seconds.
Frequently Asked Questions
How accurate is "220 − age"?
±10-15 bpm for any individual. The formula was derived in 1971 from a small sample and never validated rigorously. Tanaka's "208 − 0.7 × age" is more accurate for older adults. A field test (running uphill all-out for 3 min) gives the most reliable number.
Do beta-blockers affect my zones?
Yes — beta-blockers lower max heart rate by 20-30 bpm, making age-based formulas inaccurate. Use perceived effort or talk-test instead.
Why is my chest strap reading different from my watch?
Optical wrist sensors are 5-10% less accurate than chest straps, especially during interval workouts when HR changes rapidly. For zone training, chest straps remain the gold standard.