Health⏱ 6 min read
How to Calculate Your Heart Rate Zones for Training
Training in the right heart rate zone makes the difference between productive effort and junk miles. Here's how to calculate your max heart rate, define your five zones, and know which zone to use for each training goal.
Heart rate zones turn subjective effort into objective training. Instead of "I worked hard," you know exactly what physiological system you were targeting. Here's the science and the calculations.
Finding Your Maximum Heart Rate
Heart rate zones are calculated as percentages of your maximum heart rate (MHR). The simplest estimate:
MHR = 220 − Age (Fox formula — most widely used)
Example: 35 years old
MHR = 220 − 35 = 185 bpm
More accurate formula (Tanaka, 2001):
MHR = 208 − (0.7 × Age)
35 years: 208 − (0.7 × 35) = 208 − 24.5 = 183.5 bpm
Both are estimates. Individual variation is ±10–15 bpm. A measured MHR from a true all-out effort (e.g., the last 30 seconds of a maximal hill sprint) will be more accurate than any formula.
The Five Training Zones
Zone% of MHRFeelPurpose
Zone 1 — Recovery50–60%Very easy, conversationalActive recovery, warm-up
Zone 2 — Aerobic base60–70%Easy, could singFat burning, aerobic base, long runs
Zone 3 — Aerobic70–80%Moderate, talking in sentencesAerobic endurance, tempo effort
Zone 4 — Threshold80–90%Hard, short sentencesLactate threshold, race pace
Zone 5 — Maximum90–100%All out, can't speakVO2 max, speed, intervals
Worked Example: 40-Year-Old Runner
MHR = 220 − 40 = 180 bpm
Zone 1: 50–60% = 90–108 bpm
Zone 2: 60–70% = 108–126 bpm
Zone 3: 70–80% = 126–144 bpm
Zone 4: 80–90% = 144–162 bpm
Zone 5: 90–100% = 162–180 bpm
Heart Rate Reserve Method (More Precise)
The Karvonen formula uses your resting heart rate (RHR) for greater precision. Measure RHR first thing in the morning before getting out of bed for three days and average the results.
Heart Rate Reserve (HRR) = MHR − RHR
Target HR = RHR + (% intensity × HRR)
Example: MHR 180, RHR 55, targeting Zone 2 (60–70%):
Lower: 55 + (0.60 × 125) = 55 + 75 = 130 bpm
Upper: 55 + (0.70 × 125) = 55 + 87.5 = 142.5 bpm
vs simple % method: 108–126 bpm
The Karvonen zones are shifted up for a fit person with low RHR.
The Zone 2 Paradox
Most recreational athletes train too hard. Zone 2 — genuinely easy aerobic effort — feels embarrassingly slow, so people drift into Zone 3 thinking they're working harder and therefore getting more benefit. Research and elite coaching increasingly supports the "80/20" rule: around 80% of training volume at Zone 1–2, with only 20% at Zone 4–5. Zone 3 is the "junk miles" zone — hard enough to accumulate fatigue, not hard enough to drive the specific adaptations of threshold or VO2 max work.
Zone 2 Markers (If You Don't Have a HR Monitor)
- You can hold a full conversation without gasping
- Nasal breathing is comfortable throughout
- You feel like you could continue indefinitely
- You finish the session feeling energised, not depleted