Target heart rate zone calculator
Training in the right heart-rate zone matches your effort to your goal — recovery, fat-burning, aerobic base, threshold, or peak performance. This calculator turns your age (and optionally your resting pulse) into all five training zones expressed in beats per minute, so you know what to aim for on a watch or chest strap.
How it works
Maximum heart rate is estimated with the Tanaka formula, which fits population data better than the older 220 − age rule:
HRmax = 208 − 0.7 × ageYou then choose how the zone targets are built:
- % of max HR:
target = intensity% × HRmax. Simpler, no resting pulse needed. - Karvonen (heart-rate reserve):
target = restingHR + intensity% × (HRmax − restingHR). The reserve (HRmax minus resting) accounts for your fitness, so it personalises the lower zones in particular.
| Zone | Intensity | Purpose |
|---|---|---|
| 1 — Very light | 50–60% | Warm-up, recovery |
| 2 — Light | 60–70% | Endurance base (fat burn) |
| 3 — Moderate | 70–80% | Aerobic / cardio fitness |
| 4 — Hard | 80–90% | Anaerobic / performance |
| 5 — Maximum | 90–100% | Short intervals |
Worked example
A 30-year-old gives HRmax = 208 − 0.7 × 30 = 187 bpm. Using Karvonen with a resting heart rate of 60 bpm, the heart-rate reserve is 187 − 60 = 127 bpm. The bottom of Zone 3 (70%) is 60 + 0.70 × 127 ≈ 149 bpm, and the top (80%) is 60 + 0.80 × 127 ≈ 162 bpm.
Using percentage of max (no resting HR needed), Zone 3 would be 70% × 187 = 131 bpm to 80% × 187 = 150 bpm — noticeably lower because the method does not account for the fact that this person’s resting rate sits well below the average. The Karvonen method gives more personalised results for anyone with an atypically high or low resting heart rate.
What each zone feels like — and when to use it
The numbers on a heart-rate monitor are more useful when you know what the zones feel like from the inside:
Zone 1 (50–60% intensity) feels like a gentle walk. You can hold a full conversation easily. Use it for warm-up, cool-down, and active recovery days between hard sessions.
Zone 2 (60–70%) is a comfortable aerobic pace — you can speak in full sentences but would not choose to hold a lengthy phone call. Often called the “fat-burning zone” because at this effort level the body draws proportionally more energy from fat stores. This is the bread-and-butter zone for base endurance building: long slow runs, easy cycling, steady rowing.
Zone 3 (70–80%) is a moderate aerobic effort, often called the “cardio zone.” Speech becomes laboured — a few words at a time. Sustained Zone 3 builds cardiovascular efficiency and is common in moderate-distance training sessions.
Zone 4 (80–90%) is hard: breathing is fast and speech is essentially impossible. This is threshold training — the intensity at which lactate accumulates faster than it clears. Interval sessions, tempo runs, and hard cycling climbs live here. Short sessions in Zone 4 build the most fitness per minute, but they also require the most recovery.
Zone 5 (90–100%) is maximum effort, sustainable for only seconds to a couple of minutes. Sprint intervals, VO₂ max intervals, and hill sprints. The body is working anaerobically. Use sparingly and always with adequate recovery.
A note on the fat-burning zone misconception
Zone 2 burns a higher proportion of calories from fat, but that does not mean it burns the most fat in absolute terms. A hard Zone 4 session burns more total calories per minute and therefore more total fat in absolute grams, even though the proportion from fat is lower. Zone 2 is still valuable — it is sustainable for long durations, easy to recover from, and builds the aerobic base that supports all harder training — but “fat-burning zone” can mislead people into thinking easy exercise is better for body composition than hard exercise. Both have a place in a well-rounded training plan.
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