Target Heart Rate Calculator

The Target Heart Rate calculator computes five training zones from your Age and Resting Heart Rate using the Karvonen formula (heart-rate reserve). It first derives Max HR = 220 − age and HR Reserve = Max HR − resting HR, then distributes the reserve across Rest, Fat Burn, Cardio, Peak, and Maximum zones.

1. Enter Age (1–120 years) in the first field. 2. Enter Resting Heart Rate (30–120 bpm) in the second field. 3. Click Calculate. The result lists five zones in order — Rest, Fat Burn, Cardio, Peak, Maximum — each with a min–max bpm range.

Each zone's bpm range is computed as rhr + hrReserve × fraction, where hrReserve = (220 − age) − rhr. Rest: 0–50% of reserve. Fat Burn: 50–60%. Cardio: 60–70%. Peak: 70–85%. Maximum: 85–100% (capped at Max HR = 220 − age). Bounds are Math.floor'd, and the lower bound of each zone is the previous upper bound + 1 so zones are contiguous. Example: age 30, resting 70 → Max 190, reserve 120, Peak zone ≈ 155–172 bpm.