Triathlon Heart Rate Training Zones with the Karvonen Method
Heart rate zones let you train each triathlon session at the intensity it is meant to develop — easy aerobic base, tempo, threshold, or VO2max — instead of guessing by feel. This calculator builds your five zones with the Karvonen (heart rate reserve) method, which anchors every zone to both your maximum heart rate and your resting heart rate.
The formula
The Karvonen equation for a target heart rate at a given intensity is:
Target HR = Resting HR + Intensity% × (Max HR − Resting HR)
The quantity (Max HR − Resting HR) is your heart rate reserve (HRR) — the working range of your heart between complete rest and all-out effort. Because HRR subtracts your resting heart rate, a fit athlete with a low resting pulse gets different zones than someone with the same max HR but a higher resting pulse. That is why Karvonen is preferred over a flat "percentage of max HR" for endurance training.
Estimating maximum heart rate
If you have not measured your true max HR in a lab or a maximal field test, the calculator estimates it:
- Tanaka: Max HR = 208 − 0.7 × age. Derived from a large 2001 meta-analysis, it fits population data more accurately across ages, especially for masters athletes over 40.
- Classic: Max HR = 220 − age. Simple and familiar, but it can be off by 10–12 bpm for any individual and tends to overestimate for younger athletes and underestimate for older ones.
Both are estimates. Whenever you have a genuinely measured max HR — for example the highest value seen at the end of a hard hill-repeat or 5K test — enter it in the optional field to override the estimate.
The five zones
Zones are expressed as a percentage of heart rate reserve:
- Zone 1 — Recovery (50–60% HRR): Very easy spinning or jogging for warm-ups, cool-downs, and recovery days.
- Zone 2 — Endurance (60–70% HRR): The aerobic base zone. For most triathletes, roughly 70–80% of total training volume sits here because it builds mitochondrial and capillary density without heavy fatigue.
- Zone 3 — Tempo (70–80% HRR): "Comfortably hard" steady efforts that develop aerobic power and race rhythm.
- Zone 4 — Threshold (80–90% HRR): Around lactate threshold; the pace you can hold for roughly an hour. Key for Olympic- and 70.3-distance race pacing.
- Zone 5 — VO2max (90–100% HRR): Maximal aerobic efforts done only in short intervals to raise your ceiling.
Worked example
A 35-year-old with a resting heart rate of 60 bpm: Tanaka max HR = 208 − 0.7 × 35 = 208 − 24.5 ≈ 184 bpm. Heart rate reserve = 184 − 60 = 124 bpm. Zone 2 lower bound = 60 + 0.60 × 124 = 60 + 74.4 ≈ 134 bpm; upper bound = 60 + 0.70 × 124 = 60 + 86.8 ≈ 147 bpm. So this athlete's endurance zone is about 134–147 bpm.
Swim, bike, and run differ
Heart rate at the same effort is usually lower in the water than on the bike, and lower on the bike than running — often by 5–10 bpm per discipline — because of body position, the cooling effect of water, and the smaller muscle mass involved in swimming. Many triathletes set discipline-specific zones rather than applying one set of run-based numbers to all three sports.