The Five Heart Rate Zones
| Zone | % Max HR | Effort | Training Benefit |
|---|---|---|---|
| 1 — Warm-Up | 50-60% | Very easy | Recovery, warm-up |
| 2 — Fat Burn | 60-70% | Comfortable | Endurance base, fat oxidation |
| 3 — Aerobic | 70-80% | Moderate | Cardiovascular fitness |
| 4 — Threshold | 80-90% | Hard | Speed, lactate threshold |
| 5 — Maximum | 90-100% | All-out | Peak performance, VO2max |
The Karvonen Method
This calculator uses the Karvonen formula, which accounts for your resting heart rate. Two people the same age with different fitness levels get different zone numbers. That makes it more useful than simply multiplying max heart rate by a percentage.
Target HR = ((Max HR − Resting HR) × Intensity%) + Resting HR
Max HR ≈ 220 − Age
Which Zone Should You Train In?
Zone 2 (60-70%) — Where most endurance training should happen. Running or cycling at a conversational pace. This builds your aerobic base, burns fat efficiently, and can be sustained for hours. Most recreational athletes spend too little time here.
Zone 3 (70-80%) — The "tempo" zone. Uncomfortable but sustainable for 20-60 minutes. Good for general fitness but easy to overdo. Many runners spend too much time here when they should alternate between zone 2 and zone 4.
Zone 4 (80-90%) — Threshold training. Hard intervals of 5-20 minutes. This is where you build speed and push your lactate threshold higher. Effective but demanding—limit to 1-2 sessions per week.
Zone 5 (90-100%) — Sprint intervals. Maximum effort for 30 seconds to 3 minutes with full recovery between sets. Builds peak power and VO2max. Very taxing—use sparingly.
The 80/20 Rule
Elite endurance athletes spend about 80% of training time in zones 1-2 and 20% in zones 4-5. Most recreational athletes do the opposite—spending too much time at moderate intensity (zone 3). Going easier on easy days and harder on hard days produces better results than always training at medium effort.