Heart-rate zones turn 'go easy' and 'go hard' into precise, trainable targets. Knowing your five zones lets you structure cardio for the adaptation you actually want.
Max HR and the two methods
We estimate maximum heart rate with the Tanaka formula. Zones can then be set as simple percentages of max, or — if you provide a resting heart rate — via the more individualised Karvonen (heart-rate reserve) method.
How to distribute training
A polarised split — roughly 80% easy aerobic work and 20% hard — is well supported for building endurance without burning out. Most people ride too hard on easy days and not hard enough on hard days.
Frequently asked questions
We use the Tanaka formula: 208 − 0.7 × age, which is more accurate than the old '220 − age'. For a true figure, a supervised max-effort test is best.
Karvonen uses your heart-rate reserve (max HR − resting HR) to set zones, personalising them to your fitness. Target HR = reserve × intensity% + resting HR.
Zone 2 burns the highest proportion of fat, but higher zones burn more total calories. For fat loss, overall calorie balance matters more than the zone you train in.