Find Your Target Heart Rate Zone

What the Karvonen Heart Rate Calculator Does

This calculator finds your target heart rate for exercise using the Karvonen method, which is based on your heart-rate reserve rather than a simple percentage of your maximum heart rate. You enter your age, your resting heart rate, and the training intensity you want to work at, and it returns the beats-per-minute (bpm) range you should aim for.

It is useful for runners, cyclists, and anyone doing cardio who wants to train in a specific zone, such as fat-burning, aerobic base, or threshold work. Because the formula accounts for your resting heart rate, it tends to give more personalized zones than methods that ignore your fitness level.

How the Karvonen Formula Works

The Karvonen method starts with your heart-rate reserve (HRR), which is the gap between your maximum heart rate and your resting heart rate. You then take a percentage of that reserve and add your resting heart rate back in. The full formula is:

Target HR = ((220 - age) - resting HR) x intensity% + resting HR

Here, (220 - age) is the common estimate of your maximum heart rate, and (220 - age) - resting HR is your heart-rate reserve. Intensity is written as a decimal, so 60% becomes 0.60. To get a training zone, you run the formula twice, once at the low end of the intensity range and once at the high end.

A Worked Example

Suppose you are 40 years old with a resting heart rate of 65 bpm and you want to train at 60% to 70% intensity.

First, estimate maximum heart rate: 220 - 40 = 180 bpm. Then find heart-rate reserve: 180 - 65 = 115 bpm.

At 60%: 115 x 0.60 = 69, then 69 + 65 = 134 bpm. At 70%: 115 x 0.70 = 80.5, then 80.5 + 65 = 145.5 bpm (about 146). So your target zone is roughly 134 to 146 bpm.

Choosing the Right Intensity Zone

Different intensity ranges support different goals. These are common starting points, not strict rules:

• 50-60%: very light, good for warm-ups and recovery days
• 60-70%: easy aerobic base building and longer, comfortable sessions
• 70-80%: moderate to vigorous, improves aerobic capacity and endurance
• 80-90%: hard, threshold and tempo work for experienced athletes
• 90-100%: maximal efforts and short intervals, used sparingly

Tips and Common Mistakes

Measure resting heart rate correctly. Take it first thing in the morning before getting out of bed, ideally averaged over a few days. Using a daytime or post-coffee reading inflates the number and shifts your zones.

Remember that 220 - age is only an estimate of maximum heart rate, with a typical error of around 10 to 12 bpm from person to person. If you have a measured maximum from a lab test or a hard field effort, use that figure instead for more accurate zones.

Convert intensity to a decimal before multiplying, and do not forget to add resting heart rate back at the end. A frequent error is taking a flat percentage of (220 - age), which ignores heart-rate reserve and gives lower, less personalized targets.

Factors That Affect Your Result

Your numbers can shift over time and from day to day. As your fitness improves, your resting heart rate often drops, which changes your heart-rate reserve and your zones. Recalculate periodically.

Heat, dehydration, caffeine, stress, illness, and certain medications such as beta-blockers can all change your heart rate at a given effort. On those days, pay attention to how you feel rather than chasing exact numbers. If you have a heart condition or are new to exercise, check with a doctor before setting intensity targets.