Heart Rate Zones: free running heart rate zones calculator.
Run a 30 minute test, or type in your lactate threshold heart rate. Get your seven running zones in beats per minute.
Friel's running zones
- Zone 1under 85% of LTHRUnder 140 bpm
- Zone 285 to 89% of LTHR140 to 148 bpm
- Zone 390 to 94% of LTHR149 to 156 bpm
- Zone 495 to 99% of LTHR157 to 164 bpm
- Zone 5a100 to 102% of LTHR165 to 169 bpm
- Zone 5b103 to 106% of LTHR170 to 175 bpm
- Zone 5cover 106% of LTHROver 175 bpm
Hand it to your AI
Your AI can check these numbers against your training and adjust them. The prompt has your results filled in.
See the prompt
My lactate threshold heart rate for running is 165 bpm, from a 30 minute solo time trial (the average of the last 20 minutes). With Joe Friel's running zones that gives: Zone 1 under 140 bpm, Zone 2 140 to 148 bpm, Zone 3 149 to 156 bpm, Zone 4 157 to 164 bpm, Zone 5a 165 to 169 bpm, Zone 5b 170 to 175 bpm, Zone 5c over 175 bpm. Look at my recent runs, tell me how much time I spend in each zone, and plan my next two weeks of runs with these zones.
Gemini, Grok Bot, Dots, Muse and Cue: copy the prompt and paste it in.
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How it works
How the Heart Rate Zones works.
Zones built on your lactate threshold heart rate, or LTHR, come from a test you run, not from your age. Joe Friel, the coach who wrote The Triathlete's Training Bible, publishes a way to find LTHR without a lab, and a set of running zones built on it.
The test: warm up, then run 30 minutes as hard as you can hold, on your own and not in a race. Press lap 10 minutes in. Your average heart rate over the last 20 minutes is your LTHR. Pace it evenly: going too hard in the first few minutes and fading gives a wrong number.
Friel's running zones are shares of LTHR. Zone 1 is under 85%, Zone 2 is 85 to 89%, Zone 3 is 90 to 94% and Zone 4 is 95 to 99%. Zone 5 splits in three: 5a is 100 to 102%, 5b is 103 to 106% and 5c is above 106%.
This calculator rounds each zone to whole beats and runs one zone straight into the next, so every heart rate falls in exactly one zone. Friel sets run and bike zones apart, so find your threshold for each sport on its own.
The formula
- zone bounds = LTHR × 85%, 90%, 95%, 100%, 103% and 106%
- LTHR = average heart rate for the last 20 minutes of a 30 minute solo run
The science
Where the numbers come from.
Every number on this page links to the paper it comes from. How Memory.fit uses the science
Friel J. Joe Friel's Quick Guide to Setting Zones. TrainingPeaks, May 4, 2012, updated 2026.
Coaching article · 2012 · Read it
Example
A worked example.
A runner whose average heart rate over the last 20 minutes of a 30 minute test was 165 bpm.
- 1LTHR is 165 bpm, so Zone 5a starts at 165.
- 2Zone 1 is under 140 bpm, and Zone 2 is 140 to 148 bpm.
- 3Zone 3 is 149 to 156 bpm and Zone 4 is 157 to 164 bpm, just under your LTHR.
- 4Zone 5b is 170 to 175 bpm, and Zone 5c is anything over 175.
Questions
Heart Rate Zones: questions.
Run 30 minutes as hard as you can hold, alone, not in a race. Press lap at 10 minutes. Your average heart rate for the last 20 minutes is your LTHR.
Friel's guide puts it plainly: 220 minus your age is as likely to be wrong as right. A threshold test measures you, so the zones fit you.
No. Friel gives the bike and the run different zone percentages and says to set your threshold for each, because your zones in each sport are a little different. This calculator is for running.
That depends on your plan and your race, and coaches differ. Your AI can read your runs, see where your time actually goes, and set each session's zone with you.
Friel suggests testing early in your base and build periods. Retest the same way each time, so the numbers compare, and when your zones stop matching how your runs feel.
Not medical advice. These numbers come from published research on groups of athletes. Your own needs can differ; talk to a doctor or a sports dietitian about any health condition.