About the Heart Rate Zone Calculator
Most zone calculators run 220−age, print five crisp numbers, and let you believe them. The formula they used has a standard deviation of about ±12 beats per minute — a third of people are further off than that. This tool is the honest version: Karvonen zones from your measured resting heart rate as the primary method, Tanaka’s better-fitting 208−0.7×age beside the classic formula, and a measured max — the one number that beats every formula — used the moment you have one.
The zones themselves are the standard five, mapped to what they are for rather than to marketing colours. Engine validated in Node against textbook Karvonen worked examples before shipping.
The scatter is the honest part: the 220−age formula carries a standard deviation of roughly ±12 bpm across the population, and Tanaka’s regression, while it fits the population better, is similar for an individual. A measured max makes both columns irrelevant — subscribers get the field-test protocols below.
Heart rate runs lower on the bike than running at the same effort (less muscle mass working), with rowing between. Offsets: cycling −7 bpm, rowing −3 bpm on the zone boundaries.
A wallet-sized card with your five zones and the talk-test cues — for the gym, the bike bag, or taped to a treadmill.
How to Use the Heart Rate Zone Calculator
Enter your age, your resting heart rate if you know it, and a measured maximum if you have one. The tool builds the standard five training zones using the best information you gave it — Karvonen heart-rate-reserve zones when resting HR is present, plain percent-of-max otherwise — and it always tells you which method it used and how much to trust the numbers.
The Five Zones, and What They Are Actually For
- Zone 1 — Recovery (50–60% HRR). Genuinely easy movement. Its job is blood flow on the day after hard work, not fitness. If it feels pointless, it is working.
- Zone 2 — Base (60–70% HRR). The famous one. Conversational effort that builds the aerobic engine: mitochondria, fat oxidation, stroke volume. Most of a well-built week lives here.
- Zone 3 — Tempo (70–80% HRR). “Comfortably hard.” Useful in doses; also the zone entire training careers accidentally sink into, hard enough to tire you, too easy to sharpen you.
- Zone 4 — Threshold (80–90% HRR). The edge of what you can sustain. Raises the lactate threshold: the pace you can hold for an hour of racing.
- Zone 5 — VO2 (90–100% HRR). Short, hard intervals near max. Big returns, big recovery costs; a little goes a long way.
Why the Formulas Deserve Error Bars
The 220−age rule dates to the early 1970s and was never intended as an individual prescription; its population scatter is roughly ±12 bpm. Tanaka and colleagues’ 2001 regression (208 − 0.7 × age) across 351 studies fits the average person better, especially past forty, but any formula collapses the population onto a line you may not sit on. This tool treats formulas as what they are — starting estimates — and treats a measured max, from a hard race finish or a proper field test, as the real answer.
The Karvonen Difference
Percent-of-max zones ignore the floor. Karvonen zones are percentages of the span between resting and maximum — heart-rate reserve — so two athletes with the same max but resting rates of 45 and 75 get appropriately different zones. Since resting heart rate falls as fitness improves, Karvonen zones also quietly update as you do, which is why the tool asks for a current resting number rather than the one you remember from years ago.
Related tools: the Pace Calculator for translating zones into splits, the VO2 Max Calculator for the engine-size estimate, and the Calorie Burn Calculator for what the session cost. Browse every Health & Fitness tool for more.
General fitness information, not medical advice. Formulas estimate; individuals vary; medication (beta-blockers especially) changes heart-rate response entirely. Talk to a clinician before hard maximal efforts if you have any cardiac history, symptoms, or a long layoff behind you.
Frequently Asked Questions
Why does this ask for resting heart rate?
Because the Karvonen method — zones as percentages of heart-rate reserve, the span between resting and maximum — accounts for fitness in a way plain %-of-max cannot. Two people with a max of 185 but resting rates of 45 and 75 are in very different places, and Karvonen zones reflect that. If you skip resting HR, the tool falls back to %HRmax and says so.
How accurate is 220 minus age?
Not very, and this is the number most zone calculators hide: the formula's standard deviation is roughly ±12 beats per minute, meaning about a third of people are more than 12 bpm off their formula value. Tanaka's 208 − 0.7 × age fits population data better, especially past 40, but it carries similar individual scatter. That is why the zones here show ranges built on both, and why a measured max — from a hard race finish or a field test — beats either formula.
What is zone 2, and why does everyone talk about it?
Zone 2 is steady aerobic work — hard enough to count, easy enough to hold a conversation. The attention is deserved: large volumes of it build the aerobic base (mitochondrial density, fat oxidation, cardiac output) that everything else sits on, and it is the intensity most recreational athletes accidentally skip by training every day slightly too hard. The practical test: you can speak in full sentences. If you can only manage short phrases, you have drifted into zone 3.
Should zones differ between running and cycling?
Yes, a little. Heart rate runs roughly 5–8 bpm lower on the bike than running at the same effort, because less muscle mass is working and the position differs; rowing sits between. Subscribers get per-sport offsets applied to their zones. The bigger point: zones anchored to a running max are slightly too high for the bike, which quietly turns easy rides into tempo.
Is heart rate even the right thing to train by?
It is the most accessible good signal, with known quirks: it lags effort by a minute or two (bad for short intervals), drifts upward in heat and dehydration, and is suppressed by fatigue. Power (cycling) and pace (running on flat ground) respond instantly; heart rate tells you what the effort costs. Using heart rate for easy days and long efforts, and pace/power/feel for short hard intervals, is the boring consensus that works.
