Heart rate zones are ranges of beats per minute (bpm) linked to different training effects, from easy recovery to all-out efforts. They are useful because heart rate responds to effort regardless of terrain, wind or fatigue, whereas pace does not. But zones are only as good as the numbers you feed into them, so it pays to understand where the formulas come from and how much error they carry.
This guide is general information, not medical advice. Heart rate-based training assumes a healthy heart. If you take medication that affects heart rate (for example beta blockers) or have a heart condition, get individual guidance from your doctor.
Step 1: estimate maximum heart rate
Maximum heart rate (HRmax) is the highest rate your heart reaches during an all-out effort. It mostly depends on age and genetics, not on fitness.
| Formula | Equation | Age 30 | Age 40 | Age 50 |
|---|---|---|---|---|
| Classic (Fox, 1971) | 220 − age | 190 | 180 | 170 |
| Tanaka et al. (2001) | 208 − 0.7 × age | 187 | 180 | 173 |
Tanaka, Monahan and Seals published their equation in the Journal of the American College of Cardiology in 2001, based on a meta-analysis of 351 studies and a lab study. It predicts slightly lower values than 220 − age for young adults and higher values after 40, where the classic formula tends to underestimate. ACSM’s Guidelines for Exercise Testing and Prescription (current edition) list both, with Tanaka’s as the more accurate option.
Neither formula is personal: the standard deviation is roughly 10–12 bpm, so two 40-year-olds can have true maxima of 165 and 195. If you already run regularly and have no health concerns, the highest value you see in the last minute of a hard 5K race, or at the top of a few hard uphill repeats, is a better field estimate.
Step 2: measure resting heart rate
Resting heart rate (RHR) is needed for the reserve method. Measure it lying down right after waking, before coffee, for 60 seconds, on three to five mornings, and take the average. A typical adult range is 60–100 bpm; trained endurance athletes often sit in the 40s or 50s. A morning value 5–10 bpm above your normal can be a sign of illness, poor sleep or accumulated fatigue.
Step 3: choose a method
Percentage of max heart rate
The simplest method: zone limits = HRmax × percentage. It ignores resting heart rate, so it is fine for beginners but less individual.
Heart rate reserve (Karvonen)
Heart rate reserve (HRR) is HRmax − RHR. The Karvonen formula (1957) sets targets as:
Target HR = HRR × intensity % + RHR
ACSM uses %HRR to define intensity: moderate is roughly 40–59% HRR and vigorous 60–89% HRR. Because %HRR tracks percent of oxygen uptake reserve closely, it is the preferred method in exercise prescription.
The 5-zone model
Most watches and apps use five zones. The percentages below are common reference values; different brands shift the edges by a few percent.
| Zone | Name | % HRmax | % HRR | Feels like | Use |
|---|---|---|---|---|---|
| 1 | Recovery | 50–60% | 50–60% | Very easy, full conversation | Warm-up, recovery days |
| 2 | Aerobic / easy | 60–70% | 60–70% | Easy, can talk in sentences | Most training, long runs |
| 3 | Tempo | 70–80% | 70–80% | Moderate, short sentences | Steady runs, marathon pace |
| 4 | Threshold | 80–90% | 80–90% | Hard, few words | Tempo and threshold intervals |
| 5 | VO2max | 90–100% | 90–100% | Very hard, no talking | Short intervals, finishing kicks |
Note that the same percentage gives different bpm values depending on method, as the next example shows.
Worked example: a 40-year-old runner
Age 40, resting heart rate 60 bpm.
- HRmax (Tanaka) = 208 − 0.7 × 40 = 208 − 28 = 180 bpm (220 − 40 gives the same 180 at this age).
- HRR = 180 − 60 = 120 bpm.
| Zone | % HRmax method | Karvonen (% HRR) method |
|---|---|---|
| 1 (50–60%) | 90–108 | 120–132 |
| 2 (60–70%) | 108–126 | 132–144 |
| 3 (70–80%) | 126–144 | 144–156 |
| 4 (80–90%) | 144–162 | 156–168 |
| 5 (90–100%) | 162–180 | 168–180 |
Check one line: zone 2 lower limit with Karvonen = 120 × 0.60 + 60 = 72 + 60 = 132 bpm; upper limit = 120 × 0.70 + 60 = 84 + 60 = 144 bpm. With the %HRmax method the same zone is 180 × 0.60 = 108 to 180 × 0.70 = 126 bpm. That 24 bpm difference explains why two apps can disagree about your “zone 2”. Enter your own values in our heart rate zone calculator to see both versions.
Zones from lactate threshold heart rate (LTHR)
Max heart rate formulas say nothing about your fitness. Lactate threshold heart rate does: it is roughly the highest heart rate you can sustain for about an hour. A common field test popularised by coach Joe Friel: after a good warm-up, run 30 minutes alone as hard as you can evenly sustain, and take the average heart rate of the last 20 minutes as your LTHR.
| Zone | % of LTHR | Example, LTHR 165 bpm |
|---|---|---|
| 1 Recovery | < 85% | < 140 |
| 2 Aerobic | 85–89% | 140–147 |
| 3 Tempo | 90–94% | 148–155 |
| 4 Sub-threshold | 95–99% | 156–164 |
| 5 Above threshold | ≥ 100% | ≥ 165 |
Arithmetic: 165 × 0.85 = 140.3, 165 × 0.90 = 148.5, 165 × 0.95 = 156.8. LTHR zones are especially useful for experienced runners and should be retested every 6–8 weeks during a training block. If you also want an aerobic fitness estimate, our VO2max calculator works from a race time or a field test.
How to use zones in practice
- Build most of your week in zone 2. Polarised training research (Seiler, 2010) shows endurance athletes spend about 80% of training at low intensity. Our marathon training plan guide applies this.
- Expect cardiac drift. On long or hot runs heart rate creeps up 5–15 bpm at the same pace. Slow down to stay in zone, or accept the drift on purpose.
- Use effort and the talk test as a cross-check. Beginners in our beginner 5K plan can rely on the talk test alone.
- Remember the lag. Heart rate takes 1–2 minutes to rise during short intervals, so judge 30–60 second repeats by pace or effort.
Wearable accuracy
Optical sensors on the wrist measure blood flow under the skin. Validation studies, such as Shcherbina and colleagues (Journal of Personalized Medicine, 2017), found most wrist devices measured heart rate with errors under about 5% at steady state, while calorie estimates were far less accurate. Errors grow with rapid intensity changes, cold skin, tattoos, a loose band or arm movements that match your cadence. Chest straps using electrical (ECG-like) signals remain the most accurate consumer option. Wear the watch snugly, one finger above the wrist bone, and treat sudden jumps at the start of a run with suspicion.
Sources
- Tanaka H., Monahan K.D., Seals D.R. (2001), Journal of the American College of Cardiology: age-predicted maximal heart rate revisited.
- American College of Sports Medicine: ACSM’s Guidelines for Exercise Testing and Prescription (current edition) and Garber C.E. et al. (2011) position stand on exercise quantity and quality.
- Karvonen M.J. et al. (1957): the effects of training on heart rate.
- Shcherbina A. et al. (2017), Journal of Personalized Medicine: accuracy of wrist-worn devices.