Heart Rate Reserve Calculator
Calculate heart rate reserve with our free tool. See your stats, compare against averages, and track progress over time.
Reviewed by Sher, Sports Science & Nutrition Specialist
Formula
HRR = Max HR - Resting HR | Target HR = (HRR x %Intensity) + Resting HR
Heart Rate Reserve is the difference between max and resting HR. Target training HR uses the Karvonen formula multiplying HRR by desired intensity and adding resting HR.
Worked Examples
Example 1: 30-Year-Old Recreational Runner
Problem:A 30-year-old with a resting heart rate of 65 bpm wants training zones using the Karvonen method.
Solution:Max HR (Fox) = 220 - 30 = 190 bpm\nHRR = 190 - 65 = 125 bpm\nZone 2 (60-70%): Low = 125*0.60+65=140, High = 125*0.70+65=153\nZone 4 (80-90%): Low = 125*0.80+65=165, High = 125*0.90+65=178
Result:HRR: 125 bpm | Zone 2: 140-153 | Zone 4: 165-178 | Fitness Level: Good
Example 2: 50-Year-Old Beginning Exerciser
Problem:A 50-year-old with resting heart rate of 80 bpm needs safe exercise intensity zones for starting an exercise program.
Solution:Max HR (Fox) = 220 - 50 = 170 bpm\nHRR = 170 - 80 = 90 bpm\nZone 1 (50-60%): Low = 90*0.50+80=125, High = 90*0.60+80=134\nZone 2 (60-70%): Low = 90*0.60+80=134, High = 90*0.70+80=143
Result:HRR: 90 bpm | Recommended Zone: 125-143 bpm | Fitness Level: Average
Frequently Asked Questions
What is heart rate reserve and why is it important?
Heart rate reserve (HRR) is the difference between your maximum heart rate and your resting heart rate, representing the total range of heart rate available for physical exertion. This metric was popularized by Finnish physiologist Martti Karvonen and serves as the foundation for the Karvonen method of calculating target training heart rates. HRR is important because it accounts for individual fitness levels, unlike simple percentage-of-max-HR calculations. Two people with the same maximum heart rate but different resting heart rates will have different HRR values, leading to more personalized and accurate training zones. Athletes and coaches use HRR to prescribe exercise intensity that matches the desired physiological training effect.
How does the Karvonen formula calculate target heart rate?
The Karvonen formula calculates target heart rate using the equation Target HR equals the product of Max HR minus Resting HR multiplied by desired intensity percentage plus Resting HR. This approach is more individualized than simply multiplying maximum heart rate by a percentage because it factors in your current fitness level through resting heart rate. For example a person with a max HR of 190 and resting HR of 60 has an HRR of 130. To train at 70 percent intensity you compute 130 multiplied by 0.70 plus 60 which equals 151 bpm. The Karvonen method more closely correlates with percentage of VO2max, making it the preferred method among exercise physiologists for prescribing training intensity levels.
What are the five heart rate training zones?
The five standard heart rate training zones divide exercise intensity into distinct physiological ranges. Zone 1 at 50 to 60 percent HRR is the recovery zone for warm-ups and active recovery between hard sessions. Zone 2 at 60 to 70 percent HRR is the fat-burning and aerobic base zone where your body primarily uses fat for fuel and builds endurance foundation. Zone 3 at 70 to 80 percent HRR is the aerobic zone that improves cardiovascular efficiency and moderate endurance. Zone 4 at 80 to 90 percent HRR is the anaerobic threshold zone where lactate accumulates faster than it can be cleared building speed endurance. Zone 5 at 90 to 100 percent HRR is the maximum effort zone for short burst intervals developing peak power and neuromuscular efficiency.
How do I accurately measure my resting heart rate?
The most accurate resting heart rate measurement should be taken first thing in the morning before getting out of bed, after a full night of sleep, and before consuming caffeine or engaging in any physical activity. Place two fingers on your radial artery at the wrist or carotid artery at the neck and count beats for a full 60 seconds. Alternatively use a heart rate monitor or fitness tracker that records overnight data and provides a reliable average. Take measurements on three to five consecutive mornings and average the results for the most reliable figure. Factors that temporarily elevate resting heart rate include stress, illness, dehydration, alcohol consumption, medication, and poor sleep quality. A consistent morning measurement routine eliminates most of these confounding variables.
References
Reviewed by Sher, Sports Science & Nutrition Specialist · Editorial policy