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Heart-Rate Reserve: 220-Age Model

Explore the arithmetic of a legacy heart-rate-reserve model with preset or custom intensity percentages.

  • Formula & worked example
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Calculator inputs

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How to use this calculator

  1. Enter the known values in the units shown. Results update as you type.
  2. Where results are editable, change one to solve backwards. Lock a value to hold it fixed.
  3. Use the worked example to check the method. Reset restores the starting fields.

Private by default

Inputs and results stay in this browser tab. Bookify does not upload or store the values you enter.

Formula and method

Age 40, resting pulse 60 and intensity 55% yield a modeled pulse of 126 bpm.

Modeled HR = resting HR + intensity fraction × (220 − age − resting HR).

Worked example

Enter these known values and leave the other values blank.

Age
40 years
Resting heart rate
60 bpm
Reserve percentage
55 %
Modeled pulse
126 bpm

Assumptions and limitations

  • This adult arithmetic model estimates maximum pulse as 220 minus age; it does not measure an individual maximum or prescribe a safe workout. Preset percentages are midpoints of the captured ranges; terms such as fat-burning or red-line are legacy names, not guarantees of a physiological zone. Medication, illness, training status and measured maximum can materially affect appropriate targets.
  • Clear an unknown before solving an available inverse branch, and lock independent known values when comparing measurements. Use compatible units; a one-way score or lookup does not supply an inverse.

Common questions

What does this result represent?

This adult arithmetic model estimates maximum pulse as 220 minus age; it does not measure an individual maximum or prescribe a safe workout. Preset percentages are midpoints of the captured ranges; terms such as fat-burning or red-line are legacy names, not guarantees of a physiological zone. Medication, illness, training status and measured maximum can materially affect appropriate targets.

Can I work backward from an answer?

Where the captured equation supplies an inverse, clear the unknown and enter independent known values. Rounded scores, one-way outputs and fixed lookup choices do not uniquely recover inputs.

References

Bound the adult 220-minus-age model to positive heart-rate reserve and intensity from 0 through 100 percent.

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