If you have tested your actual max HR, enter it here. Otherwise, the calculator estimates using 220 minus your age.
Calculation Method
The Karvonen method accounts for your resting heart rate, providing more personalized zones. The percentage method is simpler but less accurate for trained athletes.
Training Zones
Enter your details and click calculate.
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Introduction
Training without heart rate zones is like driving without a speedometer. You are moving, but you have no idea whether you are in the right zone for your goal. Zone 2 training (approximately 65 to 75% of maximum heart rate) has received renewed clinical attention following research by cardiologist and longevity physician Peter Attia and others citing its role in building mitochondrial density and metabolic efficiency. A 2023 review in the Journal of Physiology confirmed that the majority of elite endurance athletes spend 75 to 80% of their training volume in low-intensity zones (1 and 2) and only 10 to 20% in high-intensity zones (4 and 5). For recreational athletes, the tendency is opposite: too much time at medium intensity (Zone 3, the "junk miles" zone) and too little at either polarized extreme. This calculator computes your five heart rate training zones using the Karvonen formula (which uses heart rate reserve and is more accurate than simple maximum heart rate percentage methods) and your lactate threshold heart rate, giving you the zone boundaries in beats per minute for your specific cardiovascular profile.
What This Calculator Does
This heart rate zone calculator uses the Karvonen formula (Heart Rate Reserve method) to compute five training zones. You enter your resting heart rate and maximum heart rate (or age-estimated max). The calculator returns zone boundaries in beats per minute, the physiological target for each zone, and the ideal training time distribution for three common training goals: general fitness, fat loss, and endurance performance.
The Formula
The Karvonen formula uses Heart Rate Reserve (HRR) rather than raw maximum heart rate. HRR = Max HR - Resting HR. This accounts for individual fitness level: two people with the same max HR but different resting heart rates (50 vs 70 bpm) have different absolute heart rates at the same relative intensity. Zone 1 (50-60% HRR) is active recovery. Zone 2 (60-70% HRR) is aerobic base. Zone 3 (70-80% HRR) is aerobic threshold. Zone 4 (80-90% HRR) is lactate threshold. Zone 5 (90-100% HRR) is VO2 max and neuromuscular.
Step-by-Step Example
Determine your max heart rate
Best method: a field test (run a 1-mile time trial at maximum effort or a 3-minute all-out cycling test) with a HR monitor. If unavailable, use the revised formula: 208 - (0.7 x age). Example: 35-year-old: 208 - 24.5 = 183.5, round to 184 bpm. Note: the old 220 - age formula has a standard error of 12 bpm and frequently overestimates max HR in older adults.
Measure resting heart rate
Measure before getting out of bed in the morning after a full night's sleep. Take the average of three consecutive mornings. Example: 58 bpm resting HR. HRR = 184 - 58 = 126 bpm.
Calculate zone boundaries
Zone 1 (50-60% HRR): (126 x 0.50) + 58 = 121 bpm; (126 x 0.60) + 58 = 134 bpm. Range: 121-134 bpm. Zone 2 (60-70%): 134-146 bpm. Zone 3 (70-80%): 146-159 bpm. Zone 4 (80-90%): 159-171 bpm. Zone 5 (90-100%): 171-184 bpm.
Plan training distribution
Polarized training approach (research-supported for endurance): 75-80% of weekly training time in Zones 1-2, 5-10% in Zone 3, 10-20% in Zones 4-5. For a 5-hour weekly training volume: 3.75-4 hrs in Z1-2, 30-45 min in Z3, 1-1.25 hrs in Z4-5.
Real-World Use Cases
Beginner Runner Building Aerobic Base
A new runner who gets out of breath talking during runs is likely spending most time in Zone 3 or higher. Their zones: max HR 175, resting HR 72, HRR 103. Zone 2 ceiling: (103 x 0.70) + 72 = 144 bpm. This means intentionally slowing down to keep HR below 144 bpm, which initially requires run-walk intervals. Eight weeks of Zone 2-focused training measurably increases the pace at which they hit Zone 2, building aerobic efficiency.
Recreational Cyclist Targeting Fat Loss
Zone 2 training is often cited for fat oxidation because at this intensity, fat provides a higher percentage of fuel. A 45-year-old male cyclist (max HR 170, resting HR 55, HRR 115) calculates Zone 2 at 124 to 136 bpm. Two 45-minute Zone 2 rides per week, verified by HR monitor, optimize fat substrate use without the cortisol spike and appetite stimulation associated with high-intensity sessions.
Triathlete Race Pacing Strategy
An Ironman triathlete needs to pace a 180 km bike leg within their Zone 3 ceiling to have legs for the marathon. Their Zone 3 upper boundary (80% HRR): (max 175 - rest 48) x 0.80 + 48 = 149.6 bpm. If they exceed 150 bpm on the bike, they will exceed their lactate threshold and accumulate fatigue that compromises the run. The HR monitor set to alarm at 152 bpm becomes their race pacing tool.
Comparison
| Zone | % HRR (Karvonen) | Physiological Effect | Fuel Source | Perceived Effort (RPE) |
|---|---|---|---|---|
| Zone 1 (Recovery) | 50% - 60% | Active recovery, blood flow | Fat dominant | 1-2/10, very easy |
| Zone 2 (Aerobic Base) | 60% - 70% | Mitochondrial density, fat oxidation | Fat / some carbohydrate | 3-4/10, conversational |
| Zone 3 (Tempo) | 70% - 80% | Aerobic threshold, lactate clearance | Equal fat/carbohydrate | 5-6/10, somewhat hard |
| Zone 4 (Threshold) | 80% - 90% | Lactate threshold increase, VO2 improvement | Carbohydrate dominant | 7-8/10, hard |
| Zone 5 (VO2 Max) | 90% - 100% | VO2 max, neuromuscular, anaerobic | Carbohydrate only | 9-10/10, maximal |
Common Mistakes to Avoid
Using 220 minus age to estimate max heart rate and treating the result as accurate. This formula has a standard deviation of plus or minus 12 bpm, meaning a true max HR of 190 bpm could be estimated anywhere from 178 to 202 bpm. A 12 bpm error shifts every zone boundary by 10 to 12 bpm, potentially placing Zone 3 training at what is actually Zone 4 intensity. Field-testing max HR is strongly recommended.
Training by pace or power without cross-referencing heart rate. Pace and power outputs change with heat, fatigue, altitude, and illness while heart rate responds to the actual physiological load. A runner who runs the same pace in a 30C summer run versus a 15C spring run is working at very different HR zones. HR is the more reliable intensity proxy in variable conditions.
Spending the majority of training time in Zone 3. Zone 3 feels productive because it is moderately hard, but research by Stephen Seiler and others shows the polarized model (lots of Zone 1-2, minimal Zone 3, some Zone 4-5) produces superior adaptations for most recreational and elite endurance athletes compared to threshold-dominant approaches.
Not remeasuring zones as fitness improves. A well-trained athlete whose resting heart rate drops from 68 to 52 bpm over six months has meaningfully changed their HRR. Zone boundaries must be recalculated with the new resting HR. Without recalculation, the zones shift lower than actual and the athlete trains at lower relative intensity than intended.
Frequently Asked Questions
Accuracy and Disclaimer
Heart rate zone calculations are based on estimated or entered maximum heart rate values and the Karvonen heart rate reserve formula. Individual cardiac response to exercise varies significantly. Individuals with cardiovascular disease, arrhythmias, or any cardiac history should have exercise intensity prescribed by a cardiologist or certified exercise physiologist. This calculator is not a substitute for medical clearance before beginning an exercise program.
Conclusion
The most common training error is spending 70% of sessions in Zone 3, the moderate-intensity range that is neither easy enough to build aerobic base efficiently nor hard enough to produce meaningful high-intensity adaptations. Use these zones to structure a polarized training week. After establishing your zones, pair with the Hydration Calculator to match your fluid replacement to the sweat rate specific to each zone's intensity level, and the Calorie Deficit Calculator to estimate your training day caloric needs by zone.
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