Heart Rate Zone Calculator

1. Choose % of Max HR, Heart-rate reserve (Karvonen), or % of threshold HR (LTHR).
2. Enter the inputs shown for that method.
3. Review or edit the lower and upper percentages for each zone.
4. Select Calculate zones. After a successful calculation, the result panel scrolls into view.

Choose a method and enter your values

• % of Max HR: calculates each boundary as a percentage of Max HR. Zone HR = Max HR × zone %
• Heart-rate reserve (Karvonen): uses Max HR and resting heart rate. HRR = Max HR − Resting HR, then Zone HR = (HRR × zone %) + Resting HR.
• % of threshold HR (LTHR): uses the LTHR value you enter. Zone HR = LTHR × zone %.

For % of Max HR and Heart-rate reserve (Karvonen), choose a Max HR source: Estimate: 220 − age, Estimate: 208 − (0.7 × age), or Manual entry (measured Max HR). The initial source is Estimate: 220 − age. Estimate options show an age field; manual entry shows Measured Max HR (bpm).

For Heart-rate reserve (Karvonen), enter Resting heart rate (bpm). For % of threshold HR (LTHR), enter Lactate threshold heart rate - LTHR (bpm). Use a measured or tested value; the interface gives a 30-minute time-trial average for the last 20 minutes as an example. The calculator does not measure or estimate LTHR.

Review zone percentages and restore defaults

The percentage table has five editable zones: Very light / recovery, Light / endurance, Moderate / aerobic, Hard / threshold, and Maximum / anaerobic. Edit any lower or upper percentage before calculating. The same table is used with the selected method.

Select Reset percentages to defaults to restore the default percentage table. The separate Reset control clears the four input fields, returns the Max HR source to Estimate: 220 − age, restores the default percentages, and hides the result. It does not change the selected method.

Custom percentages must be non-negative, and each zone's upper percentage must be greater than its lower percentage. The script does not require the zones to be contiguous, non-overlapping, or within 0–100%.

Validation and calculation errors

Enter required values as whole numbers within the accepted range. The calculator shows validation feedback when a value is missing, invalid, out of range, or ordered incorrectly.

• Age: 1–120.
• Measured Max HR (bpm): 60–240.
• Resting heart rate (bpm): 20–150.
• Lactate threshold heart rate - LTHR (bpm): 60–240.
• For Heart-rate reserve (Karvonen), Max HR must be greater than resting heart rate.

Read, copy, or download the results

The result shows the selected method, its formula, and five zone ranges. Heart-rate boundaries are displayed as whole bpm values. For the Karvonen method, the result also shows Max HR, resting heart rate, and HRR.

The result includes a disclaimer: the calculation does not assess medical or cardiovascular safety, diagnose a condition, or account for medication effects.

Select Copy result to copy the generated text. If clipboard access fails, the interface displays Could not copy - select and copy manually.

Select Download zone table (.txt) to save a plain-text file containing the method, formula, zone rows, and disclaimer. It does not include every headline input or the full method table.

Limitations and calculator data handling

• Age-based Max HR values come from the selected formula and may not match your measured Max HR.
• The LTHR method requires a measured or tested value that you supply.
• Custom ranges may overlap or leave gaps because the script does not enforce contiguous or non-overlapping zones; the implementation does not state whether that is recommended.
• The calculator does not provide a medical or cardiovascular safety assessment, diagnose conditions, or account for medication effects.
• The calculator arithmetic runs in the page script using the values entered for the calculation. This statement applies to the calculator values, not to other page features such as analytics or the subscription form.

Frequently asked questions