Heart Rate Reserve & Karvonen Zone Calculator

Heart Rate Training Zones Guide

What's the difference between Karvonen Method and Simple % Max HR?

Simple method: training zone = % of maximum HR. Karvonen method: training zone = resting HR + (% × heart rate reserve). Heart rate reserve (HRR) = max HR − resting HR. Example: age 35, resting HR 62, max HR 185. HRR = 185 − 62 = 123. Zone 2 at 60-70% HRR: 62 + (0.60 × 123) to 62 + (0.70 × 123) = 136-148 bpm. Simple % max HR: 60-70% of 185 = 111-130 bpm — significantly lower. The Karvonen method personalises zones to your individual cardiovascular fitness, making the zones more accurately reflect

What should I know about Zone 2 Training — The Foundation?

Zone 2 (60-70% HRR, typically 120-145 bpm for most adults) is aerobic base training — the intensity where fat is the primary fuel and metabolic adaptations are maximised. Benefits: improves mitochondrial density, enhances fat oxidation, builds aerobic base, enables faster recovery between hard sessions. The 80/20 rule: elite endurance athletes perform approximately 80% of training in Zone 2 and only 20% in higher zones. Most recreational athletes train too hard, spending too much time at a moderate-but-not-easy intensity that's neither restful enough to recover from nor hard enough to drive top-end fitness gains.

What do I need to know about Maximum Heart Rate?

The classic formula 220 − age is only an estimate with a standard deviation of approximately 10-12 bpm — meaning a 35-year-old's actual max HR is anywhere from 163-205 bpm with high probability. More accurate formulas: Tanaka (2001): 208 − (0.7 × age) — recommended by ACSM. Gellish (2007): 207 − (0.7 × age). The only truly accurate way to find your max HR is through a maximal exercise test — sprinting all-out up a hill until you cannot continue, or during a competitive race near the end. Many runners find their true max HR is noticeably different from age-based formula estimates, which is why a real test is worth doing if precise zone training matters to you.

What should I know about Training with Heart Rate Zones?

Training log: record every workout's average and maximum HR. Progressive overload: as aerobic fitness improves, the same pace becomes a lower heart rate — a sign that Zone 2 training is working. Overtraining indicators: resting HR elevated by 5+ bpm above normal, feeling tired rather than energised, declining performance. Annual periodisation: build aerobic base in Zone 2 for months before adding Zone 4-5 work. Wrist-based optical heart rate sensors on smartwatches are convenient but less accurate than a chest strap, particularly during high-intensity intervals or in cold weather.