About the Karvonen formula
The Karvonen formula is a widely used method for setting a target exercise heart rate. Instead of taking a flat percentage of your estimated maximum heart rate, it works from heart rate reserve (HRR) — the difference between your maximum heart rate and your resting heart rate — so the target reflects your own cardiovascular fitness, not just your age. The formula is: Target heart rate = ((HRmax - HRresting) x %intensity) + HRresting.
How the calculation works
- Maximum heart rate (HRmax) is estimated with the common Fox formula, 220 minus age. If you have a measured maximum heart rate from a supervised graded exercise test, use that instead for a more accurate result.
- Heart rate reserve (HRR) is HRmax minus your resting heart rate, measured first thing in the morning before getting out of bed for the most stable baseline.
- The target heart rate at a given intensity is HRR multiplied by the intensity percentage, then added back to resting heart rate — this is what distinguishes the Karvonen method from a simple percent-of-max calculation.
Putting the result in context
Most training guidance expresses intensity as a range rather than a single number: roughly 50-60% of HRR for light activity, 60-70% for moderate or fat-burning effort, 70-80% for aerobic or cardio conditioning, and 80-90% for hard, anaerobic effort. Pick the range that matches your goal and current fitness level, and expect your comfortable pace to change as conditioning improves.
When to consult a professional
This calculator performs the standard Karvonen arithmetic; it does not know your cardiovascular history. If you are new to exercise, are managing a heart condition, take medication that affects heart rate (such as beta-blockers), or are pregnant, talk with a healthcare provider before using a target heart rate range to guide training intensity.