Exercise Intensity Calculator Formula

Understand the math behind the exercise intensity calculator. Each variable explained with a worked example.

Use the Exercise Intensity Calculator

Formulas Used

Percentage of Max HR

pct_max_hr = exercise_hr / max_hr * 100

Percentage of HR Reserve

pct_hrr = (exercise_hr - resting_hr) / hrr * 100

Max HR Value

intensity_label = max_hr

Variables

VariableDescriptionDefault
ageAge(years)30
resting_hrResting Heart Rate(bpm)60
exercise_hrExercise Heart Rate(bpm)150
max_hrDerived value= 220 - agecalculated
hrrDerived value= max_hr - resting_hrcalculated

How It Works

Exercise Intensity Metrics

Percentage of Max HR

%MaxHR = Exercise HR / (220 - Age) x 100

Percentage of HR Reserve (Karvonen)

%HRR = (Exercise HR - Resting HR) / (Max HR - Resting HR) x 100

Intensity Levels

%MaxHR%HRRLevel <57%<30%Very light 57-63%30-39%Light 64-76%40-59%Moderate 77-95%60-89%Vigorous >95%>89%Near maximal

Worked Example

A 30-year-old with resting HR 60, exercising at 150 bpm.

age = 30resting_hr = 60exercise_hr = 150
  1. 01Max HR = 220 - 30 = 190
  2. 02%MaxHR = 150 / 190 x 100 = 78.9% (Vigorous)
  3. 03%HRR = (150 - 60) / (190 - 60) x 100 = 69.2% (Vigorous)

Frequently Asked Questions

What is a good exercise intensity?

For general health, moderate intensity (64-76% max HR) for 150 minutes per week is recommended. For fitness gains, vigorous intensity (77-95% max HR) is more effective.

Why are %MaxHR and %HRR different?

HRR accounts for resting heart rate, making it a more individualized measure. Two people with the same max HR but different resting HRs will have different %HRR values.

How do I measure exercise heart rate?

Use a heart rate monitor, fitness watch, or feel your pulse for 10 seconds and multiply by 6 during a brief pause in exercise.

Ready to run the numbers?

Open Exercise Intensity Calculator