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    Heart Rate Calculator

    Calculate your maximum heart rate and training zones

    Measure in the morning before getting up. Default: 70 bpm

    How It Works

    Overview

    A heart rate calculator estimates your maximum heart rate (HRmax) and breaks it into five training zones — recovery, easy aerobic, fat burning, threshold, and maximal effort. Training in the right zone for the right amount of time is the foundation of any structured cardio plan, whether your goal is weight loss, building endurance, or running a faster race.

    This tool uses the Tanaka formula for HRmax (more accurate than the well-known 220 − age) and the Karvonen heart-rate-reserve method for zones, which personalizes the zones to your resting heart rate. A fitter heart at rest means each zone gets shifted upward, reflecting your improved cardiovascular capacity.

    The Formula

    HRmax = 208 − 0.7 × age | Target = (HRmax − HRrest) × %intensity + HRrest

    Two formulas are doing the work:

    • Tanaka HRmax: 208 − 0.7 × age. Validated on 18,712 subjects, accurate within roughly ±7 bpm.
    • Karvonen target heart rate: (HRmax − HRrest) × intensity + HRrest, where intensity is a decimal between 0 and 1.

    The five zones (with typical purposes):

    • Zone 1 (50–60%) — active recovery, warm-up
    • Zone 2 (60–70%) — fat oxidation, easy aerobic base
    • Zone 3 (70–80%) — aerobic / tempo
    • Zone 4 (80–90%) — lactate threshold
    • Zone 5 (90–100%) — VO2 max intervals, maximal effort

    Worked Example

    For a 35-year-old with a resting heart rate of 60 bpm:

    • HRmax = 208 − 0.7 × 35 = 183.5 bpm
    • Heart rate reserve = 183.5 − 60 = 123.5 bpm
    • Zone 2 (60–70%): (123.5 × 0.6) + 60 to (123.5 × 0.7) + 60 = 134 to 146 bpm
    • Zone 4 (80–90%): 159 to 171 bpm

    A common 80/20 polarized training week for this person would be roughly 80% of training time in Zones 1–2 (under 146 bpm) and 20% in Zones 4–5 (over 159 bpm), with very little time in Zone 3.

    When to Use This

    • Designing an endurance plan — keep most easy runs in Zone 2 to build mitochondrial density without accumulating fatigue.
    • HIIT sessions — set work intervals to push heart rate into Zone 4 or 5, with recoveries dropping back to Zone 1.
    • Cycling power vs. heart rate — pair zones with FTP-based power zones for cross-validation.
    • Recovery monitoring — if your morning resting HR is 5+ bpm above your normal, take an easy day.
    • Treadmill or rowing intervals — wear a chest strap and adjust pace to hold a target heart rate band rather than a pace.

    Common Mistakes to Avoid

    • Treating predicted HRmax as exact. True max can be 15+ bpm off the formula. Do a max test if zones feel obviously wrong.
    • Skipping resting HR. Without HRrest, zones revert to a generic %HRmax that ignores your fitness level. Karvonen with real data is meaningfully better.
    • Always training in Zone 3. The "moderate" zone feels productive but produces fewer adaptations than polarized Zone 2 + Zone 4 work.
    • Wrist-optical HR during high intensity. Wrist-based monitors often mistrack above 160 bpm by 10–20 bpm. Use a chest strap for zone work.
    • Using stimulants before measuring resting HR. Caffeine alone can elevate resting HR by 5–10 bpm, throwing off the calculation.

    Frequently Asked Questions

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