Heart rate zone calculator

How heart rate training zones are calculated

A heart rate zone is a band of beats per minute tied to a percentage of effort. The calculator builds five of them from two numbers: your estimated maximum heart rate (via the Tanaka formula, 208 minus 0.7 times your age) and, if you choose the Karvonen method, your resting heart rate.

Percent of max

The simplest approach. Each zone boundary is a straight percentage of your max heart rate. Zone 2 at 60 to 70 percent for someone with a max heart rate of 180 bpm is 108 to 126 bpm: 0.60 × 180 = 108 and 0.70 × 180 = 126.

Karvonen (heart rate reserve)

This method first works out your heart rate reserve, the gap between resting and max heart rate, then takes the percentage of that gap and adds it back to your resting heart rate. For someone with a max of 180 bpm and a resting heart rate of 60 bpm, reserve is 120 bpm. Zone 2 at 60 to 70 percent: 60 + 0.60 × 120 = 132 bpm, and 60 + 0.70 × 120 = 144 bpm, noticeably higher than the straight percent of max method for the same effort level.

Karvonen versus percent of max: which method and why

Both methods use the same five percentage bands, the difference is what those percentages are applied to.

Why Karvonen is usually more accurate

Percent of max ignores fitness entirely: two people with the same max heart rate get the same zones, even if one has a resting heart rate of 45 and the other 75. Karvonen factors in your resting heart rate, which is a rough proxy for cardiovascular fitness, so a fitter person with a lower resting heart rate gets a wider, more individualised reserve to work with. Named after Finnish physiologist Martti Karvonen, who published the method in 1957, it is the more commonly recommended approach when a resting heart rate is available.

When percent of max is fine

If you do not have a reliable resting heart rate, or you are looking for a quick estimate rather than a precise prescription, percent of max is a reasonable fallback. It is also what most fitness watches default to out of the box, which is why your device's zones may not match the Karvonen numbers here.

The five zones at a glance

The percentage bands below are the same regardless of method, only the number they are applied to changes. Most weekly training time should sit in zone 2, with zones 4 and 5 kept small and deliberate.

What each zone is actually for

Zone 1 is recovery, not training in the usual sense. It is for warm ups, cool downs and the easy days between harder sessions, where the goal is blood flow without adding fatigue.

Zone 2 is where the biggest share of a well built cardio programme lives. It builds the aerobic base: more capillaries, more mitochondria, a stronger, more efficient heart, all with minimal recovery cost. See the dedicated zone 2 heart rate calculator for the detail on why coaches lean on it so heavily.

Zone 3 sits in an awkward middle ground: hard enough to add real fatigue, not hard enough to drive the biggest fitness gains for the cost. Most structured programmes use it sparingly, often called the "grey zone" for that reason.

Zone 4 is threshold work: the effort you could sustain for roughly 20 to 60 minutes at your limit. It raises the pace or power you can hold before fatigue builds sharply, and is trained in controlled, planned doses.

Zone 5 is maximal, short duration effort: sprint intervals and finishing kicks. It is the smallest, most demanding slice of a programme and needs full recovery around it.

Put together, the five zones cover a spectrum from active recovery through to all out effort, and a well built cardio week uses most of them at different points rather than sitting in just one.

How to use your zones

Zones are a training tool, not a scoreboard. The most common structural mistake is spending too much time in zones 3 and 4 and not enough in zone 1 and 2, which research on well trained endurance athletes consistently shows favours a heavily skewed split: roughly 80 percent easy, 20 percent hard, with very little in between.

Use the zones to check your easy days are actually easy (zone 1 to 2) and your hard days are actually hard (zone 4 to 5), rather than everything drifting into zone 3.

Worked zone tables for both methods

Numbers make the difference between the two methods concrete. Take a 40 year old with a resting heart rate of 60 bpm: max heart rate via Tanaka is 208 − 0.7 × 40 = 180 bpm, and heart rate reserve is 180 − 60 = 120 bpm.

Percent of max, for this person

Zone 1 (50 to 60%): 90 to 108 bpm. Zone 2 (60 to 70%): 108 to 126 bpm. Zone 3 (70 to 80%): 126 to 144 bpm. Zone 4 (80 to 90%): 144 to 162 bpm. Zone 5 (90 to 100%): 162 to 180 bpm.

Karvonen, for the same person

Zone 1: 60 + 0.50 × 120 = 120 bpm to 60 + 0.60 × 120 = 132 bpm. Zone 2: 132 to 144 bpm. Zone 3: 144 to 156 bpm. Zone 4: 156 to 168 bpm. Zone 5: 168 to 180 bpm.

Every Karvonen boundary below maximum sits above its percent of max equivalent, and the two converge at 100 percent. Below that ceiling, the size of the gap is directly tied to resting heart rate, not to the width of the reserve: a resting heart rate of 60 keeps the two methods only moderately apart here, and a higher resting heart rate, say 75, would push every Karvonen boundary further above its percent of max counterpart, because the resting value is added as a floor under each one. A lower resting heart rate pulls the two methods closer together instead.

A sample training week using these zones

Zones only matter once they are attached to actual sessions. Here is one way a five day cardio week might use all five zones, aimed at the roughly 80 percent easy, 20 percent hard split the evidence favours.

Monday: zone 2, 45 minutes

An easy run, ride or row held at the low end of zone 2. This is volume, not a workout to feel proud of finishing hard; if it feels easy throughout, it did its job.

Tuesday: zone 1, 20 to 30 minutes, or rest

Active recovery or a full rest day, depending on how the week is loading up. The goal is staying well clear of accumulating fatigue before Wednesday.

Wednesday: zone 4 intervals, 30 to 40 minutes total

A warm up in zone 1 to 2, then 4 to 6 intervals of 3 to 5 minutes at the top of zone 4, with equal or slightly longer easy recovery between reps, finished with a cool down. This is the week's hardest structured session.

Thursday: zone 2, 45 to 60 minutes

A second aerobic base session, similar to Monday, sometimes extended slightly since the legs are still relatively fresh two days after the interval session.

Friday: rest or light zone 1

A full rest day, or a short easy spin or walk, ahead of the weekend's longer or harder work.

Saturday: zone 2 to low zone 3, 60 to 90 minutes

The week's longest session, mostly zone 2 with some natural drift into low zone 3 on climbs or fatigue late in the session, which is normal and not a sign the session went wrong.

Sunday: zone 5, short and optional

For anyone with a specific event to prepare for, a small dose of zone 5 work, such as 6 to 8 short sprints with full recovery, can round out the week. Most weeks this slot can simply stay a rest day instead.

Add the time up and zone 1 and 2 dominate the week by a wide margin, zone 3 barely appears, and zones 4 and 5 stay small, deliberate and fully recovered around, which is the shape a well built cardio week is meant to take.

Why your watch might show different zones

Most consumer watches default to percent of max, often using the 220 minus age formula rather than Tanaka, and some let you enter a resting heart rate for a Karvonen style calculation buried in settings. That alone can shift every boundary by several beats per minute compared to this calculator.

Wrist based optical sensors are also less accurate than a chest strap, particularly during high intensity or upper body dominant work. If your zones and your watch disagree by more than a few beats, trust a chest strap reading over the wrist sensor, and check which formula and method your watch is actually using in its settings.

None of this means the watch is broken, it usually just means it is using different assumptions. The zones on this page are a reference point to check your device against, not a claim that your device is wrong.

Why five zones, and where the model comes from

The five zone model on this page is not the only way to split up training intensity, but it is the one that has become the default across most fitness watches, coaching apps and exercise physiology textbooks, largely because it strikes a workable balance between simplicity and usefulness.

A simpler idea than it looks

Split the full range from resting to maximal effort into five even bands and you get exactly the zones on this page. That evenness is intentional rather than physiological: your body does not experience five distinct, evenly spaced gears, but dividing the range into equal percentage steps gives coaches and athletes a shared, easy to communicate language for prescribing effort, without needing individual lab testing to define every boundary.

More precise alternatives exist, at a cost

Coaches working with lab access sometimes use zones anchored to measured physiological markers instead, such as the first and second lactate or ventilatory thresholds, which mark real shifts in how the body is producing energy rather than an arbitrary percentage cut. These threshold-based zones are more individually accurate, but they need a blood lactate test or a metabolic cart to establish, which is out of reach for the vast majority of people training on their own. The five zone, percentage based model exists precisely to make a reasonable approximation of that same idea available with nothing more than an age and, optionally, a resting heart rate.

Fewer or more zones

Some frameworks simplify further, down to three zones (easy, moderate, hard) for a quicker mental model, while others split further, into seven or more, mostly for competitive endurance athletes who need finer distinctions between, say, threshold and VO2 max efforts. Five zones is squarely the middle ground: detailed enough to separate recovery from threshold from maximal effort, simple enough to remember and actually use week to week.

The number of zones matters less than using them consistently

Whichever model a programme uses, the biggest practical gains come from making sure hard sessions are genuinely hard and easy sessions are genuinely easy, not from arguing over whether the right number of zones is three, five or seven. Five zones simply gives enough resolution to catch the most common mistake, drifting everything into a comfortable middle effort, without demanding lab equipment to set up.

Platforms do not all number zones the same way

Garmin, Zwift, TrainingPeaks and a given cycling coach can all use a five zone structure with different underlying percentages or a different reference point, some anchored to functional threshold power or pace rather than heart rate at all. A "zone 2" on one platform is not guaranteed to be the same effort as "zone 2" here, so when comparing numbers across apps, check what each one is actually a percentage of before assuming they disagree.

When to recalculate your zones

Zones built from age alone barely change year to year, but zones built with Karvonen shift whenever your resting heart rate does, which is exactly the point: they are meant to track real changes in fitness, not stay fixed forever.

After a few months of consistent training

Resting heart rate typically falls as cardiovascular fitness improves, sometimes by five to ten beats over a few months of regular training. If you started with an estimated resting heart rate or have not checked it recently, remeasuring it and rerunning the calculator will widen your Karvonen zones to reflect the fitter heart underneath them.

After a break, illness or change in medication

The opposite also holds: time off, illness or a new medication can raise resting heart rate and shrink the reserve the Karvonen method relies on. Recalculating after any of these keeps the zones honest instead of training to numbers set for a fitter or unmedicated version of yourself.

Common mistakes

Using percent of max without a resting heart rate. If you have a resting heart rate handy, Karvonen gives a more individualised, usually more accurate set of zones for the same effort.

Chasing a specific zone number instead of the feel. Heart rate lags effort by tens of seconds and can be pushed up by heat, caffeine, dehydration or poor sleep on a given day. Use the zone as a guide, not a rule that overrides how the session actually feels.

Copying someone else's zones. Two people with the same age can have very different resting heart rates and true max heart rates. Zones are personal; a training plan built around someone else's numbers is not built for you.

Never updating resting heart rate. As cardiovascular fitness improves, resting heart rate tends to fall, which shifts every Karvonen zone. Recheck it every few months, especially early in a new programme.

How coaches use a heart rate zone calculator

For a coach, zones are the language a cardio programme is written in: "zone 2, 45 minutes" means nothing until it is tied to an actual bpm range for that specific client. Calculating it once at onboarding, from a resting heart rate the client actually measured, beats using a generic age based estimate for everyone.

Scraler stores each client's zones against their profile and attaches them to every cardio session assigned, so a "zone 2" prescription always maps to the same bpm range for that client, however it is delivered. See workout programming for how sessions and targets are built per client.