The three methods, briefly
Percent of max is the simplest: each zone is a slice of your maximum heart rate, from 50 percent at the bottom of Zone 1 to 100 percent at the top of Zone 5. Its weakness is that it ignores resting heart rate entirely, so a runner with a resting HR of 42 and a runner with a resting HR of 72 get identical zones if their maxes match, even though their hearts are working from very different baselines.
The Karvonen method fixes that by working with heart rate reserve, the gap between max and resting. It applies the same percentages to that reserve and adds resting heart rate back on top, which anchors every zone to your actual working range. If your resting heart rate is unusually low or unusually high, Karvonen fits you far better than percent of max.
Lactate threshold zones skip max heart rate altogether and build the zones as percentages of your threshold heart rate. This is the method most structured training plans use, and for good reason: your max heart rate barely changes with training, but your threshold moves as you get fitter. Zones tied to threshold track your adaptation instead of your genetics.
What each zone is for
- Zone 1 (Recovery): very easy jogging or brisk walking. Use it the day after hard sessions and for warmups and cooldowns.
- Zone 2 (Aerobic base): conversational running where most of your weekly mileage belongs. This site's Zone 2 heart rate calculator is the deep dive on easy-day intensity, including the MAF formula, so start there if Zone 2 is your focus.
- Zone 3 (Tempo): steady, comfortably hard running. Useful in measured doses for marathon-pace work, but the most overused zone in recreational training.
- Zone 4 (Threshold): the effort you could race for about an hour. Cruise intervals and tempo repeats here raise the pace you can sustain.
- Zone 5 (VO2 max): short, hard repeats of roughly 2 to 5 minutes with recoveries. This is where top-end aerobic power gets built, and it should be a small, deliberate fraction of the week.
Setting zones from lactate threshold
The field test is simple but honest: after a thorough warmup, run 30 minutes all out, alone, on flat terrain or a track. Going solo matters because racing others inflates the number. Take your average heart rate from the final 20 minutes of the effort; the first 10 minutes are excluded because heart rate is still climbing to match the workload. That average is your lactate threshold heart rate, and the calculator builds all five zones from it. Retest every 6 to 8 weeks during a training block, because this is the number that improves as you adapt. Formula-based zones are a starting point no matter which method you choose; adjust them with perceived effort and race data over time.
Worked example: max 180, resting 60
Take a runner with a max heart rate of 180 and a resting heart rate of 60. Percent of max puts Zone 2 at 108 to 126 bpm. Karvonen, using the same inputs, puts Zone 2 at 132 to 144 bpm. That is a 24 bpm difference at the bottom of the range, which is why the method choice matters more than people expect. Neither answer is wrong; they draw the zone boundaries on different maps. What ruins training data is switching maps mid-season, so pick one method, set your watch to match, and interpret every run against the same boundaries.
Related tools and guides
For easy-day intensity in depth, use the Zone 2 heart rate calculator. If you need a better max HR estimate first, start with the max heart rate calculator, or try the conservative aerobic ceiling from the MAF calculator. To turn zones into paces for workouts, the training pace calculator works from a recent race result. And for a full comparison of the approaches on this page, read MAF vs Karvonen vs percent of max.
Frequently asked questions
Why do my watch zones differ from this calculator?
Watch platforms ship different defaults. Some anchor zones to percent of max heart rate, some to heart rate reserve, and some to lactate threshold, and their percentage boundaries do not always match the ones published in training literature. Many also seed max heart rate from 220 minus age, which can miss your true max by 10 or more beats. Check which method your watch uses and set the boundaries manually so the watch and your training plan agree.
Which method should I use?
If you only know your age, percent of max is the quickest starting point. If you know your resting heart rate, Karvonen is more personal because it accounts for heart rate reserve. If you are willing to do a 30 minute time trial, lactate threshold zones are the best anchor for structured training because threshold reflects your current fitness. Whichever you pick, stay consistent so your heart rate data means the same thing month to month.
Do my zones change as I get fitter?
Yes, though how much depends on the method. Max heart rate barely moves with training, so percent-of-max zones stay nearly fixed. Resting heart rate drops as you get fitter, which shifts Karvonen zones. Lactate threshold heart rate and, more importantly, the pace you can hold at threshold both improve with training, so LTHR zones are worth retesting every 6 to 8 weeks during a focused block.
Why is Zone 3 controversial?
Zone 3 is the moderately hard, steady effort most runners drift into by default. It is not useless; tempo work has a place. The problem is that it is hard enough to accumulate real fatigue but not hard enough to drive the top-end adaptations of threshold and VO2 max work. Runners who live in Zone 3 tend to feel chronically tired without getting faster, which is why most coaches push easy days down into Zone 2 and hard days up into Zones 4 and 5.
What if I do not know my resting heart rate?
Measure it: lie still for a minute first thing in the morning, before coffee or getting out of bed, and read your watch or count your pulse for 30 seconds and double it. Average three mornings. If you cannot measure it yet, use the percent of max method today and switch to Karvonen once you have a number; the resting value moves the zones enough to be worth the small effort.