What Heart Rate Should You Hit During Exercise?

Training at the right intensity makes the difference between wasted effort and genuine cardiovascular adaptation. Too easy, and your heart never gets the stimulus needed to strengthen. Too hard, too often, and you accumulate fatigue that prevents recovery and actually degrades fitness. Heart rate zones give you a science-based framework for hitting the right intensity for each training goal. Your maximum heart rate (MHR) is the ceiling of your cardiovascular output. Everything else in heart rate training is expressed as a percentage of that ceiling. The classic estimate — 220 minus your age — is widely used but has a standard deviation of ±10-12 bpm. The Tanaka formula (208 − 0.7 × age) is more accurate for adults over 40. This calculator offers both plus the Karvonen formula which uses your resting heart rate for a personalized target heart rate range. The 5 training zones correspond to distinct physiological adaptations: Zone 1 (recovery), Zone 2 (aerobic base building / fat oxidation), Zone 3 (aerobic capacity), Zone 4 (lactate threshold), and Zone 5 (VO2 max / speed development). Most endurance athletes benefit most from spending 80% of training time in Zones 1-2 and 20% in Zones 4-5 — a principle known as polarized training.