Calculate your 5 heart rate training zones using the Karvonen formula (requires resting HR for accuracy). Shows max HR, heart rate reserve, each zone's BPM range and purpose, and an estimated VO2 max.
Enter your age to calculate maximum heart rate (220 − age formula). Enter your resting heart rate measured first thing in the morning for the most accurate Karvonen zone calculation. A typical resting HR is 60–80 bpm; trained athletes are often 40–60 bpm.
The Karvonen formula uses Heart Rate Reserve (max HR − resting HR) to calculate personalised training zones. Each zone shows the BPM range, the % of heart rate reserve, the equivalent effort level, and the primary training benefit.
Zones 1–2 for recovery and aerobic base. Zone 3 for tempo and threshold. Zones 4–5 for speed and VO2 max development. The display includes an estimated VO2 max (Uth et al. formula) based on your resting and max HR ratio.
The Karvonen formula calculates target heart rate using Heart Rate Reserve (HRR): Target HR = Resting HR + (% intensity × HRR), where HRR = Max HR − Resting HR. Example: Resting HR 65, max HR 185 (age 35). For Zone 2 at 70%: Target = 65 + (0.70 × 120) = 65 + 84 = 149 bpm. This is more accurate than percentage of max HR alone because it accounts for cardiovascular fitness.
Measure immediately upon waking, before sitting up. Lie still for 1 minute, then count your pulse for 30 seconds and double it. Use your index and middle fingers on your wrist (radial pulse) or neck (carotid). For accuracy, measure for 3 consecutive days and average the results. Athletes often have resting HR under 50 bpm; a healthy adult range is 60–80 bpm. Over 100 bpm at rest warrants medical evaluation.
The 220 − age formula is a population average with a standard deviation of ±10–12 bpm — meaning 68% of people are within ±10 bpm of the formula, but 32% may be significantly higher or lower. More accurate formulas: Tanaka et al. (2001): 208 − (0.7 × age), validated in a study of 514 participants across ages 18–81. Gelish et al. (2007): 207 − (0.7 × age). This calculator uses 220 − age for simplicity; substitute your known max HR if you have tested it.
Zone 1 (50–60% HRR): Recovery, warm-up, cool-down. Zone 2 (60–70% HRR): Aerobic base, fat burning, long easy runs. Zone 3 (70–80% HRR): Moderate aerobic, comfortable but significant effort. Zone 4 (80–90% HRR): Threshold training, lactate clearance, race-pace work. Zone 5 (90–100% HRR): VO2 max intervals, maximum effort, short duration only. Most training should be in Zones 1–2 (80% of total training volume).
VO2 max is the maximum rate at which your body can consume oxygen during maximal exercise, measured in mL/kg/min. It is the gold standard of cardiovascular fitness. Average adult: 35–45 mL/kg/min. Recreational athlete: 50–60. Elite endurance athlete: 70–90+. VO2 max declines ~1% per year after age 25 without training. The Uth et al. (2004) formula estimates VO2 max as: VO2 max ≈ 15 × (Max HR / Resting HR). This is a rough estimate; VO2 max testing requires a laboratory.
Zone 2 (60–70% HRR) is often called the "fat-burning zone" because fat contributes a higher percentage of fuel at this intensity. However, total calorie burn is lower than at higher intensities. Higher intensities (Zones 3–4) burn more total calories per hour, more fat in absolute terms despite lower fat percentage, and create a larger calorie deficit. The fat-burning zone is most useful for long-duration low-intensity sessions and building aerobic base.
