Heart Rate Zone Calculator

Pure max HR percentage multiplies your max heart rate by a percentage. Karvonen uses heart rate reserve (max HR minus resting HR), then adds your resting HR back. Karvonen is more individualized because it accounts for cardiovascular fitness, so a fit person with a low resting pulse gets higher zone targets.

The 220 minus age formula was never derived from controlled research. It can be off by 10 to 20 bpm for individuals. The Tanaka formula (208 minus 0.7 x age) was validated on over 18,000 subjects and tends to be more accurate, especially for adults over 40.

Most endurance plans use 80 percent Zone 2 (easy endurance) and 20 percent Zone 4-5 (threshold and VO2max intervals). Zone 1 is for recovery days, Zone 3 should be used sparingly to avoid junk miles.

A chest strap gives the most accurate reading, but a modern optical wrist sensor works fine for Zones 1-3. For Zone 4-5 intervals where heart rate changes fast, a chest strap is more reliable.

Always use a measured max HR if you have one from a lab test or a max-effort field test. Formulas are only estimates. If your tested max is 10 bpm above the formula, your real zones shift up by roughly that amount.