Cardiac Rehab Exercise Calculator
Generate an exercise prescription for cardiac rehabilitation using heart rate reserve, RPE, and estimated METs from stress test results.
About this calculator
Target heart rate zones here use the Karvonen (heart rate reserve) method: HRR = max HR minus resting HR, and the target zone is resting HR plus a percentage of that reserve, spanning 40-85% HRR overall with narrower phase-specific bands for inpatient (Phase I, 40-60% HRR), outpatient (Phase II, 50-80% HRR), and maintenance (Phase III, 60-85% HRR) cardiac rehab. Max HR achieved on a supervised exercise stress test and resting heart rate are the only two inputs the target zone needs -- both move it directly through the Karvonen formula, with resting HR carrying slightly more weight since it is added back in after being scaled -- while age and target RPE play no role in where the zone falls; age only feeds a separate, rough estimate of peak functional capacity in METs, and RPE only feeds a separate perceived-exertion-to-intensity mapping. That METs estimate is this calculator's own simplified approximation (max HR achieved divided by age-predicted max HR, times 12) rather than a directly measured or validated METs value -- real peak METs are normally read from the treadmill protocol/speed/grade achieved or measured gas exchange during the stress test itself, not back-calculated this way.
Because the formula holds max HR fixed and divides by a smaller age-predicted denominator as age increases, entering an older age with the same measured max HR actually raises the estimated METs figure here, the opposite of the general clinical expectation that functional capacity declines with age -- a reminder that this is a rough proxy, not a substitute for the actual stress test report. Calorie estimates use the standard METs-to-kcal conversion (METs x 3.5 x body weight in kg / 200) but assume a fixed 75 kg body weight rather than the actual patient's weight, so they should be treated as illustrative rather than patient-specific.
Medical Disclaimer
This calculator is for informational and educational purposes only. It is not a substitute for professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider before making decisions about your health. Never disregard professional medical advice or delay seeking it because of results from this tool.
Inputs
Results
Target HR Zone Low (40% HRR)
103 bpm
Target HR Zone High (85% HRR)
138 bpm
How to Use This Calculator
- Enter patient age, resting heart rate, and maximum HR achieved on stress test.
- Set target RPE on the Borg 6–20 scale (11–13 is typical for cardiac rehab).
- Review Target HR Zone Low and High (bpm), Estimated METs, Duration, and Frequency.
- Use Estimated Calories/Session to counsel patients on energy expenditure goals.
How the result changes with Max HR from stress test
| Max HR from stress test | Target HR Zone Low (40% HRR) | Target HR Zone High (85% HRR) |
|---|---|---|
| 75 | 76 bpm | 81 bpm |
| 113 | 88 bpm | 107 bpm |
| 225 | 133 bpm | 202 bpm |
| 250 | 143 bpm | 223 bpm |
What each input means
- Age
- Patient age for HRmax estimation.
- Resting heart rate
- Resting HR after 5 minutes of seated rest.
- Max HR from stress test
- Peak heart rate achieved during exercise stress test.
- Target RPE (Borg 6-20)
- Target rating of perceived exertion. 11-13 typical for cardiac rehab.
What each result means
- Target HR Zone Low (40% HRR)
- Lower bound of overall cardiac rehab target zone.
- Target HR Zone High (85% HRR)
- Upper bound of overall cardiac rehab target zone.
- Estimated Peak METs
- Estimated functional capacity from stress test result.
- Exercise MET Range Low
- Lower MET target for exercise sessions (40% peak).
- Exercise MET Range High
- Upper MET target for exercise sessions (85% peak).
- Recommended Duration
- Suggested continuous exercise duration per session.
- Frequency
- Recommended exercise sessions per week.
- Est. Calories/Session
- Estimated caloric expenditure per session (assumes 75 kg).
- RPE Intensity (%VO2max)
- Rough %VO2max estimate from a straight-line scaling of the Borg 6-20 RPE scale onto 0-100%, not the published (non-linear) RPE/%VO2max correspondence table -- treat it as an evenly-spaced proxy, not a lookup of clinical reference values.
How this is calculated
Worked example, using the default values
- Identify Input Parameters4 parametersAge = 60, Resting heart rate = 72, Max HR from stress test = 150, Target RPE (Borg 6-20) = 13 = 4 input(s) provided
- Calculate Target HR Zone LowTarget HR Zone Low103 = 103
- Calculate Target HR Zone HighTarget HR Zone High138 = 138
- Calculate Estimated Peak METsEstimated Peak METs = min(20, max(1, pctAchieved * 12))11.3 = 11.3
- Calculate Exercise MET Range LowExercise MET Range Low4.5 = 4.5
Engine last updated . Checked against 1 independently-derived test — how we verify calculators. Built by Paul Gunder, a software engineer, not a licensed financial, medical, or legal professional.
Frequently Asked Questions
Why do age and target RPE not change the target heart rate zone?
The target heart rate zone comes entirely from the Karvonen formula -- resting HR plus a percentage of heart rate reserve (max HR minus resting HR) -- so only those two heart rate inputs determine it. Age instead feeds a separate estimated-METs figure, and target RPE feeds a separate RPE-to-intensity percentage; neither touches the HR zone calculation.
Why does entering an older age raise the estimated METs figure here?
This calculator estimates METs from the ratio of the measured max HR to an age-predicted max HR (220 minus age), so for the same measured max HR, an older age produces a smaller predicted denominator and therefore a higher ratio and a higher estimated METs figure -- the opposite of the general clinical pattern that functional capacity tends to decline with age. It is a mathematical property of this particular rough proxy formula, not a claim that older patients have better fitness; the actual measured METs from the stress test report is more reliable.
Why is the calorie estimate the same regardless of the patient's actual weight?
The calorie-per-session figure uses the standard METs-to-kilocalorie formula, but this calculator applies it with a fixed assumed body weight of 75 kg rather than an entered patient weight, so the result is illustrative rather than adjusted for a specific patient's actual body weight. A heavier or lighter patient at the same MET level will burn proportionally more or fewer calories than shown here.
How does the phase-specific zone differ from the overall target zone?
The overall target zone spans the full 40-85% heart rate reserve range this calculator supports, while the phase-specific zones narrow that range to match where a patient typically sits in a supervised program: 40-60% HRR for inpatient Phase I, 50-80% HRR for outpatient Phase II, and 60-85% HRR for maintenance Phase III. All three phase bands are calculated from the same resting HR and max HR entered, just at different percentage cutoffs of heart rate reserve.
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