years
bpm
Max HR (bpm)
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Heart rate zones
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Heart Rate Zones + BMI Calculator for Smarter Training

If you train with a watch on your wrist and a plan on your fridge, you already know that guessing intensity is how plateaus happen. Our Heart Rate Zones tool uses the Karvonen formula — the one that actually factors in your resting heart rate — so your easy days stay easy and your intervals actually hurt the way they should. Drop in your age, max HR, and resting HR, and you'll get five clean zones built around your real fitness, not a generic chart taped to a treadmill. Pair it with our bmi calculator to keep an eye on body composition trends as your mileage climbs or your lifts

How to use Heart Rate Zones + BMI Calculator for Smarter Training

  1. Find your max heart rate. Use a recent field test or the 220-minus-age estimate. A real test beats a formula every time, especially if you're well-trained.
  2. Measure your resting heart rate. Check it first thing in the morning before you move or grab coffee. Average it over 3-5 days for a reliable number.
  3. Plug in your numbers. Enter your age, max HR, and resting HR into the form. The Karvonen formula uses your heart rate reserve, so resting HR matters.
  4. Read your five zones. You'll get Zone 1 (recovery) through Zone 5 (VO2 max). Each shows the bpm range you should be hitting for that effort.
  5. Match zones to your sessions. Easy runs in Zone 2, tempo work in Zone 3-4, intervals in Zone 4-5. Stick to the prescription, not how you feel.
  6. Recalculate every 6-8 weeks. As fitness shifts, so does your resting HR. Update the inputs to keep your zones honest.

Frequently asked

Why use Karvonen instead of just percentages of max HR? Karvonen uses your heart rate reserve (max minus resting), which accounts for individual fitness. Two athletes the same age can have very different zones — Karvonen catches that, the simple percentage method doesn't.
How accurate is the 220-minus-age max HR estimate? It's a rough starting point and can be off by 10-20 bpm in either direction. If you're training seriously, do a proper field test or lab test for a real number.
Can I use this for cycling and running? Yes, but your max HR is usually 5-10 bpm lower on the bike than running. If you train both, calculate separate zones using sport-specific max HR values.
What's Zone 2 and why does everyone talk about it? Zone 2 is conversational pace — about 60-70% of heart rate reserve. It builds aerobic base, mitochondrial density, and fat oxidation. Boring on paper, gold over a season.
Should I track BMI alongside heart rate zones? BMI is a blunt tool for athletes since muscle skews it, but a quick bmi calculator check can flag big shifts. Pair it with a body fat calculator for a clearer composition picture.
Does this work if I'm pregnant or trying to conceive? Talk to your doctor about training intensity during pregnancy — heart rate guidelines change. Tools like a pregnancy due date calculator or ovulation calculator are useful for planning, but exertion targets should come from your provider.
How do zones tie into a calorie deficit? Lower zones burn a higher percentage of fat, but higher zones burn more total calories per minute. If you're using a calorie deficit calculator to lean out, mix zones rather than living in one.
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