Heart rate zone calculators usually just take a percentage of your max heart rate. The Karvonen method does something more useful: it factors in how fit you already are.
220 minus age vs tanaka, picking a max heart rate formula
The traditional 220-minus-age formula is well known but research suggests the Tanaka formula (208 − 0.7×age) is more accurate across a wider age range. For a 30-year-old, that's 190 bpm (traditional) versus 187 bpm (Tanaka) — a small but real difference.
Karvonen formula calculator, why resting heart rate matters
Karvonen factors in your resting heart rate (heart rate reserve) rather than just max heart rate. For a max of 187 and a resting rate of 60, the moderate zone (60-70%) works out to 136-149 bpm — a fitter person with a lower resting rate gets a meaningfully different target than someone with the same max HR but a higher resting rate.
Heart rate zones calculator, four intensity bands at once
Rather than a single target number, this calculator shows all four common zones — light, moderate, vigorous, and maximum — so you can pick the right one for whatever workout you're planning.
