Heart Rate Zones Calculator

What this calculator does & how it works

This tool builds your personal training zones in two steps. First it estimates your maximum heart rate using the long-standing population formula HRmax = 220 − age (the Fox formula). Then it applies the Karvonen method, which is more individualized than a flat percentage of HRmax because it accounts for how fit you already are.

The Karvonen formula works from your heart rate reserve (HRR), the gap between your maximum and resting heart rates: target = (HRR × intensity%) + resting HR. A fitter person with a low resting heart rate gets a wider, more accurate range than the generic version. If you leave resting heart rate blank, the calculation falls back to a simple percentage of HRmax. The five-zone model used here is the convention popularized by training systems and described by, among others, the American Heart Association.

How to interpret your results

Each zone serves a different training purpose. Zone 1 (50–60%) is very light — warm-ups and recovery. Zone 2 (60–70%) is the comfortable, conversational base that builds aerobic endurance and is where many endurance athletes spend most of their time. Zone 3 (70–80%) is moderate aerobic work. Zone 4 (80–90%) is hard, anaerobic effort that raises your lactate threshold. Zone 5 (90–100%) is near-maximal and only sustainable for short bursts.

You don't need to train in every zone every day. A common, well-supported approach is to keep most sessions easy (Zones 1–2) and add a smaller amount of hard work (Zones 4–5). To estimate the energy side of your training, pair this with our steps-to-calories calculator.

How to measure your resting heart rate

For the most accurate zones, measure your resting heart rate properly: count your pulse for a full 60 seconds first thing in the morning, before you get out of bed, across several days, and average the results. Many wearables estimate it automatically. A typical adult resting heart rate falls between about 60 and 100 bpm, and regular endurance training tends to lower it.

Limitations and when to consult a professional

The 220 − age formula is a population average that can be off by 10–20 bpm for any given person, so every number here is an approximation. True maximum heart rate is best measured under supervision in a graded exercise test. Certain medications (notably beta-blockers) lower heart rate and make these zones invalid, and conditions affecting the heart can change safe training ranges entirely. If you have a heart condition, chest pain, dizziness on exertion, or have been sedentary, talk to a doctor before starting or intensifying exercise. Stop and seek care if you feel unwell during activity. Nothing here is medical advice.

Frequently asked questions