Heart Rate Zone Calculator
Calculate your five training heart-rate zones from age and resting heart rate.
Results update as you type.
About this calculator
A heart-rate zone calculator splits your training range into five zones, from easy recovery to maximum effort. The simple method takes percentages of your maximum heart rate; the Karvonen (heart-rate reserve) method factors in your resting heart rate for more personalised targets. Zones guide how hard to work for endurance, fat burning or peak performance.
The percentage method takes shares of your maximum heart rate (220 − age). For a 30-year-old, max is 190 bpm, so zone 2 at 60–70% is about 114–133 bpm. The Karvonen method instead uses your heart-rate reserve: target = (max − resting) × intensity + resting. With a resting rate of 60, that same zone 2 becomes (190 − 60) × 0.6 + 60 to (190 − 60) × 0.7 + 60, or roughly 138–151 bpm — higher, because it is anchored to your fitness.
Use the zones to structure training: most endurance plans keep the bulk of work in the lower zones (2–3) to build an aerobic base and reserve the top zones for shorter, harder efforts. Choose Karvonen if you know a reliable resting heart rate; otherwise the percentage-of-max method needs only your age. This is general fitness guidance, not medical advice about safe exercise intensity.
Frequently asked questions
What is the difference between the two methods?
The percentage-of-max method simply takes a share of 220 − age. Karvonen uses your heart-rate reserve (max minus resting): target = ((max − resting) × intensity) + resting, which personalises the zones to your fitness.
What are heart-rate zones used for?
Zone 2 builds aerobic base and burns fat efficiently, zone 3–4 improves aerobic capacity and lactate threshold, and zone 5 develops top-end speed. Most endurance plans keep the bulk of training in the lower zones.
Do I need a resting heart rate?
Only for the Karvonen method. The percentage method needs just your age; enter a resting rate under advanced options to use the more personalised calculation.
What heart rate is zone 2?
Zone 2 is 60–70% of your maximum. For a 30-year-old with a max of 190 bpm that is about 114–133 bpm on the percentage method; the Karvonen method raises the range once you enter a resting heart rate.
How do I train in zone 2?
Keep the effort easy enough to hold a conversation — typically an easy jog, brisk walk or steady cycle. Endurance plans often spend 70–80% of training time here to build an aerobic base.
What is a fat-burning heart rate?
Lower zones, around zone 2, burn the highest proportion of calories from fat, which is why zone 2 is labelled fat burning. Higher zones burn more total calories per minute, so overall energy expenditure still matters for fat loss.
Should I use the max or Karvonen zones?
Karvonen personalises the zones using your resting heart rate, so it suits trained people with a low resting rate. If you do not know your resting rate, the percentage-of-max method needs only your age.
API — use this calculator from code
Call this calculator as a free JSON endpoint — no key required. Send the field values below as query parameters or JSON. Read the full API docs →
Endpoint
GET https://calculator.free/api/v1/heart-rate-zones/curl
curl "https://calculator.free/api/v1/heart-rate-zones/?age=30&method=max"JavaScript fetch()
const r = await fetch(
"https://calculator.free/api/v1/heart-rate-zones/?" + new URLSearchParams({
"age": "30",
"method": "max"
}));
const data = await r.json();
console.log(data.results);Results are estimates for general guidance only, not financial, medical or tax advice.