Calculator
What the Target Heart Rate Calculator does
Target Heart Rate Calculator: calculates Max HR, Fat-burn / easy low and Fat-burn / easy high from Age and Resting Heart Rate. Formula: Max HR ≈ 220 - age; target zone = resting + (max - resting) x intensity. Example: age 30 and resting heart rate 70 bpm gives max HR 190.
From Age and Resting Heart Rate, this tool derives Max HR, Fat-burn / easy low and Fat-burn / easy high. You can nudge a single number and watch the effect straight away.
Most people who open the Target Heart Rate Calculator are someone starting a new plan. A single number is most useful as a trend over time rather than a one-off judgement.
This runs client-side, which means we never receive what you enter and could not retrieve it if asked.
The method, a field-by-field reference and a worked example built from the defaults are all on this page.
What do the Target Heart Rate Calculator fields mean?
The Target Heart Rate Calculator uses 2 inputs. Pre-filled inputs double as documentation: each one shows what a reasonable value looks like.
| Field | What to enter | Default |
|---|---|---|
| Age | accepts 10 to 90 | 30 |
| Resting Heart Rate | measured in bpm; accepts 35 to 120 | 70 |
How does the Target Heart Rate Calculator work?
The 220 - age rule has a standard deviation of roughly 10 to 12 bpm, so treat zones as a range rather than a threshold.
Values are checked first: an out-of-range or non-numeric entry names the offending field instead of returning nonsense.
Worked example
These are the values the Target Heart Rate Calculator loads by default, and the result it produces from them. This is the worked example the page starts from, reproduced here so you can check the arithmetic.
| Age | 30 |
|---|---|
| Resting Heart Rate | 70 bpm |
| Max HR | 190 |
|---|---|
| Fat-burn / easy low | 142 |
| Fat-burn / easy high | 154 |
| Cardio zone high | 166 |
| What this means | Max HR ≈ 190 bpm. Easy aerobic work often sits near 142 to 154 bpm (Karvonen method). |
Target zones and the Karvonen method
There are two ways to define a target zone. The simple percentage method uses maximum heart rate alone; the Karvonen method also uses your resting rate, which makes it more individual.
| Simple percentage | max HR × intensity | 180 × 0.7 = 126 bpm |
|---|---|---|
| Karvonen (heart rate reserve) | resting + (max − resting) × intensity | 60 + (180 − 60) × 0.7 = 144 bpm |
| Heart rate reserve | max − resting | 180 − 60 = 120 bpm |
Worth knowing
- The two methods differ substantially: 126 against 144 bpm in the example above. Karvonen is generally preferred because it accounts for fitness.
- A fitter person has a lower resting rate and therefore a larger reserve, which the simple percentage method ignores entirely.
- Common zones: 50 to 60% very light, 60 to 70% light, 70 to 80% moderate, 80 to 90% hard, 90 to 100% maximum.
- Beta blockers and some other medications lower both resting and maximum heart rate, invalidating these estimates.
How to use it
- Fill in Age (10 to 90).
- Type Resting Heart Rate in bpm (35 to 120).
- Watch the results panel as you type: it recalculates on every keystroke.
- The panel reports Max HR, Fat-burn / easy low, Fat-burn / easy high, Cardio zone high and What this means.
- Copy Link puts the current inputs in the URL, so bookmarking it brings the same numbers back.
What this tool does not do
- Population-level formulas cannot account for medical conditions, medication or pregnancy.
- This is a screening estimate, not a diagnosis.
- It does not account for anything you did not enter, by definition.
- Confirm the units before you act on the output. The arithmetic is only as sound as what went in.
Frequently asked questions
Enter Resting Heart Rate in bpm. The unit is shown beside each box, and the result carries its own label, so there is nothing to convert by hand.
Age accepts 10 to 90. If a value falls outside, the tool says which field is at fault instead of guessing.
With the values loaded when the page opens, max HR comes out as 190. The figure is derived from the inputs above, so it updates whenever they do.
It never leaves the tab. The page does the work itself rather than asking a server to.
No. There is no account, no usage cap and no trial period. The site is funded by advertising rather than by charging for the tools.
The number is exact; its meaning is approximate. Two people with identical results can be in genuinely different situations, which is why this is a screening tool rather than a diagnostic one.