Target Heart Rate Calculator (Karvonen Formula)
Use your Resting Heart Rate (RHR) to find your optimal exercise intensity zones.
What is the Resting Heart Rate Calculation Formula?
While your Resting Heart Rate (RHR) is a metric you measure (usually upon waking), the Karvonen Formula is the standard mathematical approach used to calculate your target heart rate zones based on that RHR. Unlike simpler formulas, the Karvonen method accounts for your specific cardiovascular fitness level by incorporating your Heart Rate Reserve (HRR).
The formula for Heart Rate Reserve is:
HRR = (220 – Age) – Resting Heart Rate
Once you have your HRR, you calculate your target zone using:
Target HR = (HRR × Intensity%) + Resting Heart Rate
Why Resting Heart Rate Matters
A lower resting heart rate typically indicates better cardiovascular fitness and more efficient heart function. For most adults, a normal RHR ranges from 60 to 100 beats per minute. Highly trained athletes may have RHRs in the 40s or 50s. By using your RHR in calculations, you ensure your workout intensity is tailored to your actual fitness level rather than just your age.
Heart Rate Zone Examples
| Intensity Zone | Percentage | Benefit |
|---|---|---|
| Recovery | 50% – 60% | Weight management and active recovery. |
| Aerobic | 60% – 70% | Improving cardiovascular endurance. |
| Anaerobic | 70% – 85% | Increasing speed and lactate threshold. |
| Red Line | 85% – 100% | Maximum performance and sprinting. |
How to Measure Your Resting Heart Rate Correctly
- Time it right: Measure your pulse first thing in the morning, before getting out of bed.
- Find your pulse: Use two fingers (not your thumb) on your wrist (radial artery) or neck (carotid artery).
- Count: Count the beats for 60 seconds, or count for 30 seconds and multiply by two.
- Consistency: Take the average over three mornings for the most accurate figure.
Frequently Asked Questions
Is 220-Age accurate?
It is a general estimate. While widely used, individual maximum heart rates can vary. If you have a known max heart rate from a clinical stress test, use that value instead of 220-Age.
What factors affect my RHR?
Stress, caffeine, dehydration, medication, and sleep quality can all cause temporary fluctuations in your resting heart rate.