Karvonen Formula Calculator

The heart-rate-reserve (HRR) calculation uses the difference between a maximum heart rate and a resting heart rate. A scenario at a chosen fraction adds that fraction of the reserve back to the resting value.

This calculator estimates the maximum as 220 − age. American Heart Association target heart rates (12 August 2024) presents that estimate as an average guide for adults, with examples for ages 20–70. An accepted input is not proof that the estimate is valid for that person or age; this form is not a pediatric exercise assessment.
References and method last checked: 2026-09-30. Source publication or update dates are shown separately.

The Hong Kong Department of Health handbook (2012), table 4.3 states the HRR method and limits its 220 − age estimate to adults aged 19 or older. This supports the arithmetic method in its clinical context, not the five bands or every age accepted by this form.

The five percentage bands are numerical conventions in this tool. They do not measure fat oxidation, aerobic capacity, lactate thresholds, fitness or individual exercise safety.

1. Estimated maximum = 220 − age, in beats per minute.
2. HRR = estimated maximum − resting heart rate. The reserve must be positive.
3. Scenario heart rate = resting heart rate + fraction × HRR. For 70%, use 0.70.
4. Each endpoint is rounded to the nearest whole beat per minute.

Example: age 40 and resting rate 65 give maximum 180 and reserve 115 bpm. At 70%, 65 + 0.70 × 115 = 145.5, displayed as 146 bpm. This is the formula result, not an instruction to maintain that pulse.

A percentage of HRR differs from the same percentage of maximum heart rate: 70% of 180 is 126 bpm, while this HRR scenario is 146 bpm. The AHA percentage-of-maximum ranges do not validate this tool’s five HRR bands.

Measuring Resting Heart Rate (RHR)

For the most accurate resting heart rate measurement:

1. Measure first thing in the morning, before getting out of bed
2. Ensure you've had a good night's sleep
3. Measure before consuming caffeine or other stimulants
4. Take measurements over several days and calculate the average

Manual Measurement Methods

Radial Pulse (Wrist): Place your index and middle fingers on the inside of your opposite wrist, just below the base of your thumb. Count the number of beats for 60 seconds, or for 15 seconds and multiply by 4.

Carotid Pulse (Neck): Place your index and middle fingers on either side of your windpipe, in the soft groove of your neck. Apply gentle pressure and count as above.

Using Technology

Several devices can help measure heart rate with varying degrees of accuracy:

• Chest Strap Monitors: These transmit heart-rate data to a watch or smartphone
• Fitness Watches/Trackers: Convenient for continuous monitoring throughout the day and during exercise
• Smartphone Apps: Use the phone's camera and flash to detect pulse through your fingertip
• Pulse Oximeters: Clip-on devices that measure oxygen saturation along with heart rate

A monitor reports heart rate; it does not validate the age-based maximum or the suitability of a numerical interval.

The tool divides the reserve into five illustrative intervals: 50–60%, 60–70%, 70–80%, 80–90% and 90–100%. Adjacent ranges share endpoints because the same fraction is reused.

For age 35 and resting rate 60, estimated maximum is 185 and reserve is 125 bpm. The first interval is 123–135 bpm and the last is 173–185 bpm after rounding. None of these labels establishes a physiological threshold or suitable workout for an individual.

Displaying the reserve and percentage bands makes the arithmetic inspectable. It shows how a different resting value or maximum estimate changes each numerical interval.

The result does not establish exercise benefits, readiness, recovery, fat loss or injury prevention. Those questions require information beyond age and resting pulse.