First, your maximum heart rate
Zones are a percentage of your maximum heart rate. A common estimate is 208 − (0.7 × age) beats per minute (the Tanaka formula). A 40-year-old’s estimated max is about 180 bpm. It’s an estimate — individuals vary.
The five zones
- Zone 1 (50–60%) — very light; warm-up and recovery
- Zone 2 (60–70%) — light; builds endurance and fat-burning, easy to sustain
- Zone 3 (70–80%) — moderate; improves aerobic fitness
- Zone 4 (80–90%) — hard; raises speed and threshold
- Zone 5 (90–100%) — maximum; short, intense bursts only
How to train with zones
Most endurance benefit comes from spending plenty of time in Zone 2, with occasional harder Zone 4–5 intervals. If you know your resting heart rate, the Karvonen (heart-rate reserve) method personalises your zones more accurately than percentage of max alone.
A safety note
Zone targets are for general fitness, not medical advice. If you have a heart condition, take medication that affects heart rate, or feel chest pain, dizziness or unusual breathlessness, check with your clinician before high-intensity training.