Heart Rate Zone Calculator

Training without heart rate zones is like driving without a speedometer. You have a rough sense of effort, but no way to hold a target precisely or to know when you have drifted too high. The calculator above gives you all five zones, including the Zone 2 range that has become the cornerstone of endurance training.

Two ways to set your zones

The simplest method takes a percentage of your maximum heart rate. It is quick and works fine for most people. Enter your max HR and the calculator splits it into five zones.

The better method is Karvonen, which uses your heart rate reserve, the gap between your resting and maximum heart rate. By accounting for how low your resting heart rate sits, it personalises the zones to your actual fitness. Add your resting HR and the calculator switches to this method automatically. For the cleanest resting figure, read it first thing in the morning before you are up and moving.

What each zone is for

• Zone 1, recovery: very easy, used for warm-ups and active recovery.
• Zone 2, aerobic base: the workhorse zone where you build your engine. Conversational, fat-burning, and where most of your weekly volume belongs.
• Zone 3, tempo: comfortably hard, useful in moderation but easy to overuse.
• Zone 4, threshold: hard, raises your lactate threshold, run in measured doses.
• Zone 5, VO2max: very hard, builds your aerobic ceiling in short repeats.

Why Zone 2 gets the attention

Most recreational athletes spend too much time in the murky middle, around Zone 3, where sessions are tiring enough to need recovery but not stimulating enough to drive the big adaptations. Shifting that volume down into Zone 2 lets you train more, recover better, and still build the aerobic base that makes you faster.

Getting your max HR right matters here. The old 220-minus-age formula is a rough estimate and can be off by ten beats or more. A hard field test or a recent race gives you a far more accurate number to build these zones on.

For why Zone 2 works and how to actually hold it without drifting high, read the Zone 2 heart rate guide.