What are heart rate zones?
Heart rate zones divide the range between a gentle jog and an all-out sprint into five bands of effort. Because heart rate rises with the oxygen demand of your muscles, it gives a live, objective read-out of how hard your body is working — regardless of hills, wind or tired legs that make pace misleading.
Training by zone helps you do what most runners find surprisingly difficult: keep easy days genuinely easy and hard days purposeful. The five-zone model used in this calculator is the most common one and is used by major sports-watch brands, although exact boundaries vary slightly between systems.
| Zone | % max HR | Feels like | Main benefit |
|---|---|---|---|
| Z1 Recovery | 50–60 % | Very easy, full conversation | Recovery, warm-ups, active rest |
| Z2 Aerobic | 60–70 % | Easy, can talk in sentences | Aerobic base, fat use, endurance |
| Z3 Tempo | 70–80 % | Moderate, short phrases | Aerobic power, marathon-pace work |
| Z4 Threshold | 80–90 % | Hard, a few words at a time | Lactate threshold, sustained speed |
| Z5 VO2max | 90–100 % | Very hard, cannot talk | Maximal aerobic capacity, speed |
Estimating your maximum heart rate
Every zone is anchored to your maximum heart rate, so getting that number roughly right matters more than anything else. Age-based formulas are convenient but only estimate the population average — your true maximum can easily be 10–15 beats higher or lower.
| Formula | Equation | Age 25 | Age 40 | Age 55 |
|---|---|---|---|---|
| Fox (“220 − age”) | 220 − age | 195 | 180 | 165 |
| Tanaka (2001) | 208 − 0.7 × age | 190 | 180 | 170 |
| Gulati (2010, women) | 206 − 0.88 × age | 184 | 171 | 158 |
How to find your real max heart rate
If you are healthy, already training regularly and have no heart-related concerns, a field test gives a much better number than any formula. One common approach: warm up thoroughly for 15 minutes, then run 3 minutes hard, jog 2 minutes, run 3 minutes as hard as you can sustain finishing with an all-out final 30–60 seconds up a gentle hill. The highest reading, from a chest strap, is close to your maximum. The final minute of a hard 5K race gives a similar value.
Safety first. Maximal efforts are not appropriate for everyone. If you are new to exercise, over 40 and previously inactive, or have any cardiovascular symptoms or conditions, speak to a doctor before doing a max heart rate test and use a formula estimate instead.
The Karvonen method (heart rate reserve)
A simple percentage of max HR ignores how low your resting heart rate is. The Karvonen method, described by Finnish physician Martti Karvonen in 1957, applies the percentages to your heart rate reserve — the gap between resting and maximum — and then adds resting heart rate back:
target HR = resting HR + (HRR × intensity %)
Worked example
A 40-year-old with a max HR of 180 and a resting HR of 55 has a reserve of 125 beats. Zone 2 at 60–70 % is 55 + (125 × 0.60) = 130 to 55 + (125 × 0.70) = 143 bpm. Using plain % of max, the same zone would be 108–126 bpm — much lower. Fitter runners with low resting heart rates usually find Karvonen zones match their perceived effort better.
How to measure resting heart rate
Measure it in bed, just after waking and before getting up, on three to five mornings, and use the average. A resting heart rate that is 5–10 beats above your normal is a useful early warning of illness, poor recovery or overreaching.
How much time to spend in each zone
Studies of endurance athletes across many sports have found a consistent pattern: the best performers do the large majority of their training at low intensity and a small amount at high intensity, spending relatively little time in the “moderate” middle. This is often called polarised or 80/20 training.
Common heart rate training pitfalls
Cardiac drift
During long runs, especially in heat, heart rate creeps upward at a steady pace as you lose fluid and your core temperature rises. Slowing down to stay in zone is normal.
Lag in intervals
Heart rate takes 1–2 minutes to catch up with effort. For short intervals, use pace or feel and let heart rate confirm the effort afterwards.
Wrist sensor errors
Optical sensors can lock onto your cadence and read 160–180 bpm on easy runs. Suspiciously high readings are often a sensor issue — a chest strap fixes it.
Zone 2 feels too slow
Many runners have to walk hills at first to stay in Zone 2. Stick with it: aerobic fitness improves over weeks, and your Zone 2 pace will get faster.
Want a number for your aerobic ceiling? Estimate it with the VO2max calculator. Heart rate and pace work best together. Use the VDOT calculator to set pace targets for each session and check the heart rate zone matches the intended effort. Curious about energy use? The running calories calculator estimates how much fuel each run costs.
- Tanaka H, Monahan KD, Seals DR (2001). Age-predicted maximal heart rate revisited. J Am Coll Cardiol 37(1):153–156.
- Gulati M et al. (2010). Heart rate response to exercise stress testing in asymptomatic women. Circulation 122(2):130–137.
- Karvonen MJ, Kentala E, Mustala O (1957). The effects of training on heart rate. Ann Med Exp Biol Fenn 35(3):307–315.
- Seiler S (2010). What is best practice for training intensity and duration distribution in endurance athletes? Int J Sports Physiol Perform 5(3):276–291.
Last reviewed: September 2026 · Health disclaimer