A super-simple tool to help you determine 'THR' for optimal cardio training

Knowing what cardio intensity to aim for – is a big part of successfully realizing any fitness goal (including the Sensible Fitness Program).

This calculator will provide a 'range' or 'zone' – in beats per minute (BPM) – of between 50% and 85% of your Maximal Heart Rate (MHR), based on your age and condition.

Why 50 to 85? 

The most commonly recommended range to exercise within, is between 50 to 85 percent of your MHR for at least 20-30 minutes per session, to get the best results from aerobic exercise. Here, we're talking low and moderate-intensity steady state (LISS/MISS) cardio.

MHR is the upper limit of what your cardiovascular system is estimated to be able to cope with during physical activity. (There's more detail about this on the cardio training page.)

On the other hand, your anaerobic zone commences at the upper threshold of your Training Heart Rate (THR), and where you'd want to focus when doing high-intensity interval training (HIIT) cardio. (The Borg RPE scales are handy in helping you to gauge your limits.)

Okay, so how do you calculate your particular THR for low-moderate level cardio?

Simply click the blue button BELOW:

The calculations provided by this THR Calculator are based on the 'Karvonen method.'

The formula factors in resting heart rate (HRrest) to calculate target heart rate (THR) by using a range of 50–85% intensity. Therefore:

THR = ((HRmax − HRrest) × % intensity) + HR.


Since the Karvonen method takes resting heart-rate (RHR) and MHR into account, it is a relatively accurate method for estimating THR. Because a low RHR is a reliable indicator of fitness, the Karvonen formula is more successful at predicting THR zones for both 'fit' and 'unfit' individuals.