Heart Rate Zone Calculator: Three Methods, Five Zones
Enter your maximum heart rate and this works out five heart rate training zones three ways: percent of max, heart rate reserve and percent of threshold. Add a resting heart rate and a threshold heart rate to see all three side by side.
Your Zone 2 Heart Rate
- Percent of maximum heart rate115 to 133 bpm
- Heart rate reserve (Karvonen)135 to 148 bpm
- Percent of threshold heart rate (Friel)146 to 151 bpm
Three methods, three answers, and none of them is wrong. Pick one method and stay on it, because a Zone 2 run judged against a different model is not the same session.
Percent of maximum heart rate
The five-zone model Garmin and Polar ship as their default. It needs one number, your maximum heart rate, which is why almost every watch uses it.
Heart rate reserve (Karvonen)
Karvonen, Kentala and Mustala (1957). Each zone is your resting heart rate plus a share of your heart rate reserve, which is your maximum minus your resting heart rate. Every boundary moves as your resting heart rate falls. A percent of max table never does.
Percent of threshold heart rate (Friel)
Joe Friel's running zones, anchored on your lactate threshold heart rate rather than on your maximum. Threshold is the number that moves with training, and it is the one you can test yourself.
Kracey is a HYROX, running and endurance coach on Telegram. Your coach reads the zones you have set in intervals.icu and judges every session against those rather than against an age formula. When your efforts suggest the zones themselves are wrong, it says so rather than trusting them over you.
One thing to keep in mind
Zones from a formula are an estimate of where your physiology sits, not a measurement of it. They shift with heat, altitude, illness, caffeine and how much sleep you got, and the boundary between two zones is a line drawn through a gradual change rather than a switch.
If you have a heart condition, are on medication that affects heart rate, or are returning to training after a long break, speak to a doctor before working to the top two zones.
How This Heart Rate Zone Calculator Works
A heart rate zone is a band of beats per minute that corresponds to one training intensity, and five bands is the model almost every watch, coach and training plan uses. What nobody tells you is that there is no single agreed way to draw the lines. Three respected methods produce three different tables from the same athlete, and this calculator shows you all three rather than picking one quietly on your behalf.
The methods differ in what they anchor on. Percent of max hangs everything off one number. Karvonen adds your resting heart rate, so the zones move as your fitness changes. Friel anchors on your lactate threshold instead, which is the number a training block actually shifts. Use the one whose input you trust most.
Train at the intensity you meant to
Percent of Maximum Heart Rate
Each zone is a share of your maximum heart rate: 50 to 60% for Z1, then 60 to 70%, 70 to 80%, 80 to 90% and 90 to 100%. It is the default five-zone split Garmin and Polar ship, which is why it is the table most athletes have already seen. It needs one input, and that is both its strength and its weakness: if your max is a guess, every zone below it is a guess too.
Heart Rate Reserve, the Karvonen Method
Your heart rate reserve is your maximum minus your resting heart rate, and Karvonen, Kentala and Mustala set each zone at your resting heart rate plus a share of that reserve. The arithmetic matters: at 70%, a Karvonen boundary sits 30% of your resting heart rate above the percent of max boundary, so the two tables are furthest apart for an untrained athlete and closest for a fit one. The part worth having is that Karvonen zones move on their own. Take six weeks of consistent aerobic work that drops your resting heart rate from 58 to 52, and every boundary shifts down with it. A percent of max table would show you the same five numbers it showed you in January.
Percent of Threshold Heart Rate, the Friel Method
Joe Friel anchors his running zones on lactate threshold heart rate rather than on maximum: Z1 under 85% of LTHR, Z2 85 to 89%, Z3 90 to 94%, Z4 95 to 99%, and Z5 from 100% up. The appeal is that threshold is the number that responds to training, and unlike a maximum you can test it without going to complete exhaustion. Friel's own field test is a hard 30 minute effort on your own, with your average heart rate over the last 20 minutes taken as the threshold. Go alone rather than in a race, because a race start pushes the first 10 minutes too hard.
Your Zone 2 Heart Rate, and Why It Moves With the Method
Zone 2 is the easy aerobic band, the one you can hold a full conversation in and the one most athletes ride straight through because it feels too slow to be doing anything. It is where the aerobic base gets built, and in HYROX that base is what lets you run the eighth kilometre at something close to the pace of the first.
Here is the part that trips people up. The three methods put Zone 2 in three different places for the same athlete, and the gap is not small. A percent of max table and a Karvonen table can sit 15 to 20 beats apart at the same boundary, and a Friel table drawn off a threshold sits somewhere else again. So a Zone 2 number is meaningless until you say which method produced it.
The practical answer is not to find the true version. It is to pick one method, write down the five numbers, and judge every session against that one table for a whole block. Switching models halfway is how an easy run quietly becomes a tempo run.
For how Zone 2 fits a HYROX week, and what the 80/20 split actually asks of you, read our guide to HYROX training zones.
What 220 Minus Your Age Gets Wrong
The formula is a population average, and you are one person. Robergs and Landwehr traced its history in JEPonline in 2002 and found it was never derived from original research at all, but assembled from observation across roughly 11 sources. More usefully, they put a number on the error: across two decades of studies the estimate misses by 7 to 11 beats per minute. On a predicted 180 that puts your real maximum anywhere from about 170 to 190, which is more than a whole zone wide.
It is also biased, not just noisy. Tanaka, Monahan and Seals pooled 351 studies covering 18,712 people in the Journal of the American College of Cardiology and found the line of best fit was 208 minus 0.7 times your age, which means 220 minus age systematically underestimates the maximum of older athletes. A 50 year old is told 170 when the average is closer to 173, and the older you are the further the formula drifts.
So use a number you have actually seen. The highest heart rate in your own recent hard sessions, from a race finish or a set of hill repeats, beats any formula. If you have never seen a genuine maximum, start from the estimate, then correct it the first time a session goes above it, because a heart rate you recorded is evidence and a formula is not.
How to Use Your Zones
- Pick one method and stay on it for a whole training block.
- Write the five numbers into your watch, so the zones on your wrist match the zones in your plan.
- Build the week around the zones rather than the other way round:
- Z1: warm-ups, cool-downs and genuine recovery days.
- Z2: the long, steady aerobic work that should be most of your running volume.
- Z3: tempo efforts, and the zone to spend the least time in by accident.
- Z4: threshold intervals, the ones that raise the ceiling on sustainable pace.
- Z5: short, hard repeats for top-end power.
- Re-check your numbers when your resting heart rate shifts or a threshold test comes back different.
Treat the boundaries as guidance rather than as gates. Heat, altitude, poor sleep, caffeine and the first 10 minutes of any session all move your heart rate without changing what the session is doing to you.
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Frequently Asked Questions
Heart rate zones are five bands of beats per minute, each matching one training intensity, from easy recovery up to maximum effort. They give you a repeatable way to say how hard a session was, instead of guessing. The boundaries are drawn from your maximum heart rate, your heart rate reserve or your threshold heart rate, depending on which method you use.
It depends on which method you use, which is why this calculator shows you all three. On a percent of max model, Zone 2 runs from 60 to 70% of your maximum. On Karvonen it is your resting heart rate plus 60 to 70% of your heart rate reserve, which lands higher. On Friel it is 85 to 89% of your threshold heart rate. Enter your numbers above and you get all three ranges in beats per minute.
No, and it is worth knowing how far off it can be. It is a population average that misses an individual by roughly 7 to 11 beats per minute, and it was never derived from original research. It also underestimates the maximum of older athletes, because the better fit across 351 pooled studies is 208 minus 0.7 times your age. Use the highest heart rate you have actually recorded in a hard session instead.
Use the one whose inputs you trust. If all you have is a maximum, use percent of max. If you also track a reliable resting heart rate, Karvonen is better, because the zones move as your fitness changes. If you have tested your threshold, Friel is the most responsive of the three. What matters more than the choice is staying on it for a whole block.
Your maximum is the highest reading from your own hard sessions, typically a race finish or the last of a set of hill repeats. For threshold, run a hard 30 minutes on your own and take your average heart rate over the final 20 minutes. Do neither if you have a heart condition or are returning from a long layoff without speaking to a doctor first.