Your heart rate is a real-time window into how hard your body is working. Training by heart rate zones helps you exercise at the right intensity for your goal, rather than guessing — too easy and you stall, too hard and you burn out. This guide explains how the zones work and how to find yours.
Your maximum heart rate
Training zones are based on your maximum heart rate (MHR) — the highest your heart can safely beat. The classic estimate is 220 minus your age, though more refined formulas like Tanaka (208 − 0.7 × age) are often more accurate. These are population averages, so your true maximum may differ by 10–15 beats. The maximum heart rate calculator shows several estimates so you can pick a sensible figure.
The five training zones
Zones are bands of intensity as a percentage of your maximum. Roughly: Zone 1 (50–60%) is very light recovery; Zone 2 (60–70%) builds base endurance and fat-burning; Zone 3 (70–80%) develops aerobic fitness; Zone 4 (80–90%) builds speed and lactate threshold; and Zone 5 (90–100%) is maximal, sustainable only briefly. Each zone trains your body differently, so a balanced programme uses several. The target heart rate calculator gives the beats-per-minute range for each.
A more personal target: the Karvonen method
A better method, Karvonen, also uses your resting heart rate to personalise the zones to your fitness. It works on your heart-rate reserve — the gap between resting and maximum. For example, with a max of 190 and a resting rate of 60, the reserve is 130; a 70% target is 60 + 0.70 × 130 = 151 bpm. As your fitness improves and your resting rate falls, the same percentage gives a different, fitter target. The Karvonen calculator does this for you.
Train mostly easy: the 80/20 rule
One of the most consistent findings in endurance research is that fit athletes do roughly 80% of their training at easy, low-zone intensity and only 20% hard. Most amateurs do the opposite — always moderately hard — which causes fatigue without the benefits of either true rest or true intensity. Spending most sessions in Zone 2, where you can still hold a conversation, builds a bigger aerobic engine and leaves you fresh for the occasional hard effort.
Measuring your fitness over time
Two simple numbers track your cardiovascular fitness. Your estimated VO2 max reflects how well your body uses oxygen, and your heart-rate recovery — how fast your pulse drops after exercise — reflects how responsive your heart is. Both improve with consistent training and are motivating to watch. The VO2 max calculator and heart-rate recovery calculator let you follow your progress.
Building a week around the zones
Zones only help if they shape your weekly plan. A simple, effective structure for most people is three to five sessions a week: the majority as easy Zone 2 runs or rides where you can hold a conversation, one harder session in Zone 4 such as intervals, and at least one full rest or recovery day. Beginners should spend almost everything in Zones 1 and 2 for the first couple of months to build an aerobic base and let tendons and joints adapt, adding harder efforts only once easy work feels comfortable. Increase your total weekly training by no more than about 10% at a time — the classic guideline for avoiding overuse injury. As fitness improves, the same effort will sit at a lower heart rate, a satisfying sign your aerobic engine is growing, and your easy pace will naturally quicken.
Measure accurately and stay safe
A chest-strap monitor is more accurate than a wrist optical sensor for hard efforts, where wrist readings can lag or jump. Take your resting heart rate first thing in the morning for a true baseline. And spend most training in the comfortable zones — every session at maximum effort leads to fatigue and injury. If you have any heart condition or are new to exercise, get medical advice before training by heart rate. Remember too that heart rate is raised by heat, dehydration, caffeine, stress and poor sleep, so on those days the same pace will read higher — listen to your body, not only the number on your watch.