The five heart rate zones
- Zone 1 (50–60%): very light, for warm-ups and recovery.
- Zone 2 (60–70%): light, you can talk easily; builds base fitness and endurance, with a larger share of energy from fat.
- Zone 3 (70–80%): moderate to hard; improves heart and lung efficiency.
- Zone 4 (80–90%): hard, talking is difficult; raises speed and threshold.
- Zone 5 (90–100%): maximum effort, for very short intervals such as HIIT.
According to the American Heart Association, moderate intensity is about 50–70% of maximum heart rate and vigorous about 70–85%. If you enter your resting heart rate (Karvonen method), the calculator uses the American College of Sports Medicine ranges of heart-rate reserve: moderate 40–59% and vigorous 60–89%.
Note: the five zone names (light, moderate, hard) are a common training convention, not the same thing as the “moderate” and “vigorous” intensity bands in the health guidelines above. A zone called “light” can already count as moderate — or, with the Karvonen method, even vigorous — for the health bodies.
Why does resting heart rate matter?
If you enter it, the calculator uses the Karvonen method: zones are based on your heart rate reserve (max − resting), which fits your fitness level better. Fitter people have a lower resting heart rate, so their zones differ from someone else of the same age.
Frequently Asked Questions
Is the “fat-burning zone” real?
Partly. At light effort (zone 2) a larger share of the energy comes from fat, but harder effort burns more calories in the same time. For fat loss, total calories matter most; see our calories burned calculator.
How do I measure my pulse?
With a smartwatch or heart rate monitor, or by hand: place two fingers on the side of your neck or wrist, count beats for 15 seconds and multiply by 4.
Why two formulas?
“220 − age” is the best known but is inaccurate, especially for older adults. Tanaka’s formula (208 − 0.7 × age) came from a meta-analysis of many studies and is considered more accurate.