Calculator
What the Cardio Zone Calculator does
Cardio Zone Calculator: calculates Max HR, Fat-burn / easy low and Fat-burn / easy high from Age and Resting Heart Rate. Example: age 30 and resting heart rate 70 bpm gives max HR 190.
Enter Age and Resting Heart Rate and the Cardio Zone Calculator reports Max HR, Fat-burn / easy low and Fat-burn / easy high. Each change is reflected immediately, which suits quick what-if comparisons.
Context matters more than the number itself. Age, build and activity all shift it. The Cardio Zone Calculator exists to take that particular chore off your hands.
Your data stays on your machine. Once the page has loaded you could disconnect entirely and it would still work.
The meaning of each field, the formula in use, and a worked example that starts from the default inputs are all further down.
What do the Cardio Zone Calculator fields mean?
The Cardio Zone Calculator uses 2 inputs. Every box starts with a working value, so there is a real result on screen before you touch anything.
| 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 Cardio Zone Calculator work?
Each output is derived from the inputs above in a single pass; there is no hidden state carried between runs, so the same inputs always give the same calculation.
Nothing is computed until the inputs pass their checks, so you will not get a confident answer built on a typo.
Worked example
These are the values the Cardio Zone Calculator loads by default, and the result it produces from them. The figures are the tool’s live defaults and its live output, so you can reproduce them exactly.
| 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). |
How to use it
- Enter Age (10 to 90).
- Set Resting Heart Rate in bpm (35 to 120).
- The result appears as you type. There is no button to press.
- You get Max HR, Fat-burn / easy low, Fat-burn / easy high, Cardio zone high and What this means back.
- The link encodes your inputs, so saving it is enough to reproduce the result later.
What this tool does not do
- Body composition, ethnicity and age all shift what a "normal" result means.
- These formulas come from population averages and cannot account for your medical history.
- It cannot flag an input that is technically valid but wrong for your case.
- It validates ranges, not intent. A value can be accepted and still be the wrong one to use.
Frequently asked questions
Enter Resting Heart Rate in bpm. Look for the unit beside each label; the result is reported in a stated unit as well.
Age accepts 10 to 90. Out-of-range entries are refused up front, which is safer than silently clamping them.
With the values loaded when the page opens, max HR comes out as 190. That number tracks the inputs, so a small edit shows its sensitivity immediately.
Nothing is stored. The page has no back end to send data to, and holds your input only in memory.
Free, and there is no upsell. The whole tool is the free version.
Reliable as a rule of thumb, unreliable as a verdict. Equations of this kind are fitted to large groups, and the spread around the fitted line is wide enough that any individual can sit well off it.