Heart Rate Zone Calculator
Personalised training zones using the Karvonen formula
Training Zones
Based on heart rate reserve (Karvonen method)
Warm-up, cool-down, and active recovery. Very comfortable — you can hold a full conversation.
Base fitness and fat burning. The foundation of endurance training — sustainable for long sessions.
Aerobic capacity and endurance. Comfortably hard — short sentences only. Builds cardiovascular efficiency.
Lactate threshold training. Hard effort — speech is difficult. Raises the ceiling on sustainable intensity.
Peak power and anaerobic capacity. Maximum effort — unsustainable beyond short intervals. Used for sprints and HIIT.
About This Calculator
This calculator uses the Karvonen formula, which accounts for your resting heart rate to produce more personalised training zones than a simple percentage-of-max-HR approach. The formula was developed by Finnish scientist Martti Karvonen in 1957 and remains widely used in exercise science.
Maximum heart rate defaults to 220 − age when no measured value is provided. This is a population average with a standard deviation of roughly ±10–12 BPM, so individual variation is real. If you have measured your true max HR through a graded exercise test or a verified all-out effort with a heart rate monitor, enter it for more accurate zones.
Resting heart rate should be measured first thing in the morning before getting out of bed. Count beats for 60 seconds. A typical resting HR is 60–80 BPM; well-trained endurance athletes often see 40–55 BPM.
Sources: Karvonen et al. (1957), Annals of Medicine and Experimental Biology of Finland; ACSM Guidelines for Exercise Testing and Prescription.
Frequently Asked Questions
Why does resting heart rate matter?
Your resting heart rate reflects cardiovascular fitness. A lower resting HR means your heart pumps more blood per beat, giving you a larger usable heart rate reserve. The Karvonen formula incorporates this reserve so that zones better reflect actual exercise intensity for your individual physiology rather than just your age.
How do I know which zone I am in during a workout?
A heart rate monitor worn on the chest or wrist is the most reliable method. Perceived exertion works as a backup: Zone 2 lets you hold a full conversation, Zone 3 allows short phrases, Zone 4 limits you to single words, and Zone 5 makes speaking impossible.
How much time should I spend in each zone?
Most endurance coaches recommend the 80/20 rule: roughly 80% of training volume in Zones 1–2 and 20% in Zones 3–5. High-intensity work drives adaptation but demands more recovery. Excessive time in Zone 3 — sometimes called the "grey zone" — tends to accumulate fatigue without the full benefits of either true easy aerobic work or genuine high-intensity sessions.
Is 220 minus age accurate?
It is a useful population average but carries significant individual variability — roughly ±10–12 BPM at one standard deviation. Some alternatives exist (e.g. 208 − 0.7 × age from Tanaka et al., 2001), but the practical differences for most people are small. Measuring your actual maximum HR via a properly conducted maximal effort test gives the most accurate result.
Do my zones change as my fitness improves?
Yes. As aerobic fitness improves, resting heart rate typically falls. Because the Karvonen formula uses resting HR, lower values shift zone boundaries slightly upward. Recalculate every few months or whenever your resting HR changes meaningfully (more than a few beats per minute).