Heart Rate Zone Calculator

All five training zones, with what each is for.

Calculate your five heart rate training zones from maximum and resting heart rate, with the purpose and typical duration of each zone.

Written and maintained by Mohit PatelLast checked August 4, 2026How we build these

Age

years

Resting heart rate

bpm

Zone 2, aerobic base

134–146 bpm

where most endurance training should live

Zone 1, recovery122–134 bpm

Zone 3, aerobic endurance146–159 bpm

Zone 4, threshold159–171 bpm

Zone 5, maximal171–184 bpm

A common split is 80% of training time in zones 1-2 and 20% in zones 4-5, with little deliberate time in zone 3.

How the Heart Rate Zone Calculator works

The five-zone model splits training intensity into bands that produce different adaptations. Most endurance benefit comes from a large volume of easy zone 2 work plus a small amount of genuinely hard work: the middle, where it is tempting to live, produces the least per hour spent.

Also known as: training zones calculator · zone 2 heart rate · cardio heart rate zones · heart rate zones calculator · heart rate zone calculator · hr zones calculator · hr zone calculator · zone 2 calculator

Why zones exist

Different intensities of exercise produce different adaptations, and zones are a way of prescribing intensity so that the intended adaptation is the one that occurs.

Low intensity work builds capillary density, mitochondrial content and fat oxidation, and it can be accumulated in volume because it is not very fatiguing.

High intensity work drives improvements in maximal oxygen uptake and in the ability to tolerate and clear lactate, and it costs recovery. The reason to separate them is that doing everything at a moderate intermediate intensity produces less of both.

Five zones, three zones, and which to use

The five-zone model divides percentage of maximum into bands and is what most consumer devices display. It is fine for general use and the boundaries are somewhat arbitrary.

The three-zone model used in much of the endurance research divides by physiological thresholds: below the first lactate threshold, between the two thresholds, and above the second. Those boundaries correspond to genuine changes in metabolism rather than to round percentages.

For most people the practical version is simpler still: easy, where you could hold a conversation, and hard, where you could not. Most of the benefit of zone training comes from actually keeping the easy sessions easy, which requires no measurement at all beyond honesty.

Anchoring zones to something real

Zones based on predicted maximum heart rate carry the prediction's error, which can be a full zone.

Zones based on a measured maximum are better. Zones based on a measured threshold are better still, because threshold is the boundary that determines what training does and it moves with fitness in a way maximum does not.

A practical field test for threshold heart rate is a 30 minute time trial at the hardest sustainable effort, taking the average heart rate of the final 20 minutes. That figure is close to lactate threshold heart rate for most people and it can be repeated every couple of months to track change.

The lag problem

Heart rate responds to a change in effort over one to three minutes, which makes it a poor control signal for short intervals.

A 60 second hard interval will be finishing about when the heart rate reaches the intended zone, so prescribing short intervals by heart rate does not work. Pace, power or perceived effort control them properly.

For steady efforts over ten minutes or more the lag is irrelevant and heart rate works well. Matching the control variable to the duration of the effort is what makes zone training practical rather than frustrating.

Distributing training across zones

The distribution most consistently observed in successful endurance athletes puts roughly 75% to 80% of sessions in the easy zone and the remainder hard, with very little in between.

That is counterintuitive because the easy sessions feel too easy to be productive. The volume is what makes them productive, and the volume is only possible because they are easy.

The failure mode has a name: the moderate intensity trap. Sessions creep upward in intensity because they feel more virtuous, the easy days stop being easy, recovery suffers, and the hard days cannot be run hard enough. Fixing it usually means slowing the easy days down more than feels reasonable.

Where to go next

The Heart Rate Zone question rarely arrives on its own. These are the ones that usually come with it:

Target Heart Rate Calculator — Karvonen zones using your resting heart rate.
Max Heart Rate Calculator — Four formulas, because 220 minus age is the worst of them.
VO2 Max Calculator — Aerobic capacity estimated from resting heart rate or a race time.
BMI Calculator — Body mass index with category and healthy weight range.

Sources

ACSM, Guidelines for Exercise Testing and Prescription

Not medical advice. This calculator gives a general estimate, not medical advice. It cannot account for your individual health, medical history, or medication. Talk to a qualified healthcare professional before acting on any result.

Frequently asked questions

What are the five heart rate zones?

Zone 1 (50-60% of reserve) is recovery. Zone 2 (60-70%) builds aerobic base and fat oxidation. Zone 3 (70-80%) is aerobic endurance. Zone 4 (80-90%) sits around lactate threshold. Zone 5 (90-100%) develops maximal aerobic power and can only be held briefly.

Why is zone 2 training so popular?

Because it builds mitochondrial density and capillary networks with relatively little fatigue cost, so you can accumulate a lot of it. Elite endurance athletes typically spend around 80% of training time at this intensity, which is the origin of the polarised training model.

How long should I spend in each zone?

A common distribution is roughly 80% in zones 1-2 and 20% in zones 4-5, with little deliberate time in zone 3. Sessions in zone 5 are measured in minutes, not hours, a few intervals is a full workout.

Are wrist heart rate monitors accurate for zones?

At steady, moderate intensity they are usually acceptable. During intervals, weights or anything with wrist movement they lag and can misread badly, often locking onto cadence rather than pulse. A chest strap is markedly better whenever precision matters.