Heart Rate Zone Calculator

Zone 2 burns the highest percentage of calories from fat, which is why it is often called the “fat-burning zone.” However, higher-intensity zones burn more total calories per minute. For fat loss, the total calorie deficit matters most, not the fuel source during exercise. A mix of Zone 2 endurance work and higher-intensity intervals is the most effective approach for body composition.

Measure your resting heart rate first thing in the morning while still lying in bed, before coffee or any stimulation. Count your pulse at your wrist or neck for 30 seconds and multiply by two. Repeat on three consecutive mornings and average the readings for a reliable baseline.

A normal resting heart rate for adults is between 60 and 100 beats per minute. Well-trained endurance athletes often have a resting heart rate between 40 and 60 bpm. A lower resting heart rate generally indicates a more efficient cardiovascular system, though some medical conditions can also cause a low heart rate.

No. While Zone 2 is excellent for building aerobic fitness and should form the majority of your training, a mix of zones is optimal for overall performance. Polarised training, where roughly 80% of sessions are easy (Zone 1–2) and 20% are hard (Zone 4–5), is one of the most well-researched approaches for endurance development.

The Karvonen method accounts for individual fitness levels by incorporating your resting heart rate into the calculation. Two people of the same age but different fitness levels will have different resting heart rates, and therefore different heart rate reserves. This means their personalised zone boundaries will differ even though their max heart rate estimate is the same, resulting in more tailored training intensities.

Yes. Optical heart rate monitors built into smartwatches are reasonably accurate for steady-state exercise like Zone 2 running or cycling. However, they can lag during rapid heart rate changes such as interval training. For maximum accuracy during high-intensity work, a chest strap heart rate monitor is the better choice.

If you consistently cannot raise your heart rate above Zone 3, it could be a sign of overtraining, dehydration, or certain medications such as beta-blockers. Cardiac drift during long sessions can also make it harder to reach higher zones. If this is a persistent issue and not explained by medication or fatigue, consult a doctor to rule out any underlying conditions.