What is Zone 2?
Zone 2 is 60–70% of your maximum heart rate — an easy, conversational effort where you can speak in full sentences while moving. It's the cornerstone of endurance training: your body burns fat as its primary fuel, builds more mitochondria over time, and lays the aerobic base that makes every other zone possible. Most elite endurance athletes spend 70–80% of their weekly training volume here.
How long should a Zone 2 session be?
Aim for at least 45 minutes to drive meaningful aerobic adaptation; 60–90 minutes is the sweet spot most coaches target. Shorter sessions still count — what matters most is consistent Zone 2 volume across weeks and months, not any single session. Running, cycling, rowing, and swimming all qualify equally.
Choosing your MHR formula
Tanaka (208 − 0.7 × age) is the most widely validated modern formula and fits most adults better than the classic alternative. Fox (220 − age) is the original, still widely used — simple, but it tends to overestimate max HR for younger athletes and underestimate it for older ones. Gulati (206 − 0.88 × age) was derived specifically from women and is preferred when a female-specific estimate matters. All three are estimates — a lab or field test gives your true max.
MHR formula comparison
| Formula | Equation | Best for |
|---|---|---|
| Tanaka | 208 − 0.7 × age | Most adults |
| Fox | 220 − age | Classic / quick |
| Gulati | 206 − 0.88 × age | Women |
%-of-max vs Karvonen
The simple method takes a straight percentage of your max HR — the same for everyone the same age. The Karvonen method uses your heart-rate reserve (max minus resting) so a fit person with a low resting HR gets lower absolute targets than a less-fit person the same age. Tap Go advanced and enter your morning resting HR to switch. Measure it before getting out of bed for the most accurate reading.
Zone 2 vs pace-based training
Heart rate responds to heat, fatigue, and hills in ways pace can't — a hot humid day may push your HR into Zone 3 at your usual easy pace. Use HR when conditions vary and pace when you want consistent splits. If you train by pace, our Pace Calculator solves pace, time, and distance instantly.
Common questions
What is Zone 2 heart rate?
Zone 2 is the 60–70% band of your maximum heart rate — or of your heart-rate reserve with the Karvonen method. It's an easy, conversational effort that trains fat-burning efficiency and builds aerobic base.
How long should I stay in Zone 2?
Aim for 45–90 minutes per session to drive aerobic adaptation. Shorter sessions still contribute — consistent weekly Zone 2 volume matters far more than the length of any individual workout.
Which MHR formula is most accurate?
No age-based formula perfectly predicts your individual max HR — variation between people is large. Tanaka (208 − 0.7 × age) outperforms the classic Fox formula in most research. For women, Gulati is often recommended. If you know your true MHR from a field test or lab, enter it in advanced mode to override the estimate.
What is the Karvonen method?
The Karvonen method calculates zones from your heart-rate reserve — the difference between your resting and maximum heart rate. It gives personalised results: a fit person with a resting HR of 45 bpm gets lower Zone 2 targets than a sedentary person the same age with a resting HR of 75 bpm, even if both have the same max HR.
How is this different from the 5-zone calculator?
The Heart Rate Zone Calculator shows all five training zones at once. This Zone 2 calculator is purpose-built for Zone 2: your target range is the centrepiece, the three MHR formulas are easy to compare, and everything is focused on the zone that drives the most aerobic development.