Target Heart Rate Zone Calculator (Karvonen Fat Burn & Cardio Zones)
The Karvonen method calculates zones as a percentage of heart rate reserve — the gap between resting and maximum heart rate — rather than as a raw percentage of maximum. This matters because two runners with the same maximum but resting rates of 48 and 72 bpm need very different absolute paces to sit in the same physiological zone.
A resting rate of 62 bpm gives you a 124 bpm working reserve — the wider this is, the fitter your heart.
| Zone | % of HR reserve | Your range | Purpose | Typical duration |
|---|---|---|---|---|
| Zone 1 — Recovery | 50-60% | 124-136 bpm | Active recovery, warm-up | 20-40 min |
| Zone 2 — Fat burn | 60-70% | 136-149 bpm | Aerobic base, fat oxidation | 45-120 min |
| Zone 3 — Aerobic | 70-80% | 149-161 bpm | Cardiovascular efficiency | 20-60 min |
| Zone 4 — Threshold | 80-90% | 161-173 bpm | Lactate clearance, race pace | 10-30 min |
| Zone 5 — VO2 max | 90-100% | 173-186 bpm | Peak power, intervals | 1-8 min total |
Percentage of max vs heart rate reserve
The simple method (70% of max HR) ignores your baseline entirely and typically prescribes zones 8-12 bpm too low for well-trained athletes and slightly too high for deconditioned beginners. Karvonen anchors both ends of the scale to you personally, so Zone 2 stays genuinely conversational.
Which max HR formula to trust
220 minus age (Haskell) was never derived from controlled data and has a standard deviation of around 12 bpm. Tanaka's 208 − 0.7 × age fits large meta-analytic samples better, especially over 40, and Gulati's equation was validated specifically in women. A supervised ramp test still beats every formula.
Why the fat-burn zone is misunderstood
Zone 2 oxidises the highest proportion of fat, but higher intensities burn more total fat per minute because total energy cost rises. Zone 2 earns its place through mitochondrial density and capillarisation, not through the ratio printed on gym treadmills.
Estimated max heart rate and Zone 2 by age
| Age | Tanaka max HR | Haskell max HR | Zone 2 (RHR 60) | Zone 5 (RHR 60) |
|---|---|---|---|---|
| 20 | 194 | 200 | 140-154 bpm | 181-194 bpm |
| 30 | 187 | 190 | 136-149 bpm | 175-187 bpm |
| 40 | 180 | 180 | 132-144 bpm | 168-180 bpm |
| 50 | 173 | 170 | 128-139 bpm | 162-173 bpm |
| 60 | 166 | 160 | 124-134 bpm | 155-166 bpm |
| 70 | 159 | 150 | 119-129 bpm | 149-159 bpm |
People also ask
What heart rate is the fat burning zone?
Roughly 60-70% of heart rate reserve. For a 32-year-old with a resting rate of 62 bpm, that is about 137-153 bpm — an effort where you can still hold a full conversation.
Is 220 minus age accurate?
It is a rough guide with an error margin of about ±12 bpm. Tanaka's formula fits population data better, and a field or lab ramp test is more accurate than any equation.
How do I measure resting heart rate properly?
Take it immediately on waking, lying still, for a full 60 seconds — or read the overnight average from a wearable. Caffeine, alcohol, illness and poor sleep all raise it by 5-10 bpm.
Three worked examples
Same engine, three different starting points — useful if you want to see how sensitive the answer is before you type your own numbers in.
Example 1: age 24.96 years, max hr formula "Tanaka"
On the lower / more conservative end. A resting rate of 62 bpm gives you a 129 bpm working reserve — the wider this is, the fitter your heart.
Example 2: age 32 years, max hr formula "Tanaka"
A typical middle-of-the-road setup. A resting rate of 62 bpm gives you a 124 bpm working reserve — the wider this is, the fitter your heart.
Example 3: age 41.6 years, max hr formula "Haskell"
On the higher / more demanding end. A resting rate of 62 bpm gives you a 116 bpm working reserve — the wider this is, the fitter your heart.
Quick answers about the Heart Rate Zone Estimator
What exactly does the Heart Rate Zone Estimator work out?
The Karvonen method calculates zones as a percentage of heart rate reserve — the gap between resting and maximum heart rate — rather than as a raw percentage of maximum. You enter age, resting heart rate and max HR formula and the result panel updates straight away, so you can compare two or three versions of the same question in a few seconds.
What do I need before I start?
Only 3 fields: age, resting heart rate and max HR formula. Nothing else is needed and nothing is stored.
How is it calculated — percentage of max vs heart rate reserve?
The simple method (70% of max HR) ignores your baseline entirely and typically prescribes zones 8-12 bpm too low for well-trained athletes and slightly too high for deconditioned beginners. The same maths runs inside this page, so hand-checking the result on paper gives you the identical figure.
Why do two calculators give me different answers for heart Rate Zone?
220 minus age (Haskell) was never derived from controlled data and has a standard deviation of around 12 bpm. Different sites pick different assumptions, so always check which method a calculator states before you trust the gap between two numbers.
What does the "Estimated max heart rate and Zone 2 by age" table on this page tell me?
It is the reference range this tool works against — 6 rows from "20" (194) up to "70" (159). Use it to sanity-check whether the number you just calculated sits where you expected it to.
Which max HR formula should I pick?
The dropdown offers 3 choices — Tanaka, Haskell and Gulati (women). Pick the one that matches your real situation rather than the one you would like to be true; max HR formula usually moves the final figure more than any other single input, so it is worth running it twice with the option above and below your guess.
Do I have to press a button or reload the page to see the result?
No. Heart Rate Zone Estimator runs completely inside your browser, so the moment you change a value the cards recalculate — there is no submit step, no page reload and no waiting for a server round trip. That also means it keeps working on a weak or intermittent mobile connection.
Is it free, and do you keep what I type?
It is free with no sign-up, no app install and no usage limit. Nothing you enter into Heart Rate Zone Estimator leaves your device — the calculation is JavaScript running locally, so there is no upload of your figures to DrHint or anyone else.
Can I use it on a phone?
Yes — the layout stacks to a single column on small screens and the number fields open the numeric keypad on both Android and iOS. Many people bookmark this page or add it to their home screen and re-open it whenever the question comes up.
Anything to be careful about with the result?
Roughly 60-70% of heart rate reserve. Treat the output as a well-grounded estimate for planning, not as a professional, legal or medical decision on its own.
Next useful tool
Free TDEE calculator using Mifflin-St Jeor and Katch-McArdle. Get maintenance calories, a cutting target, protein/carb/fat grams and the exact date you hit your goal weight.
See how much caffeine is still in your bloodstream at bedtime. Enter your drink, the time you had it and your metabolism speed to get an hour-by-hour decay curve.
Estimate your one rep max from any set of 1-12 reps using Epley, Brzycki and Lombardi formulas, plus a full percentage training chart for bench press, squat and deadlift.
Find bedtimes and wake times that land at the end of a 90-minute sleep cycle, including fall-asleep latency, so you wake in light sleep instead of deep sleep.
Estimate body fat percentage with the US Navy circumference formula. Enter neck, waist and hip measurements to get body fat %, lean mass, fat mass and Navy standard pass/fail.
Work out ketogenic net carbs, protein and fat grams from your daily calorie budget. Includes total vs net carb maths, fibre and sugar alcohol subtraction, and a keto tier table.