Using heart rate reserve rather than a simple percentage of maximum makes the target fit your fitness level: a fitter person with a low resting heart rate gets a wider working range. The American College of Sports Medicine uses 40–59% of HRR for moderate and 60–89% for vigorous exercise.
How to use the Karvonen Formula Calculator
- Age
- Resting heart rate
- Maximum heart rate
- Measured maximum heart rate
- Exercise intensity
Results update as you type, and every field accepts the units shown in its menu.
How it works
Count your resting pulse for 60 seconds in the morning before getting up. Choose how to estimate your maximum heart rate, enter the intensity you want and the calculator adds that share of your heart rate reserve to your resting rate.
Intensity zones (ACSM)
| Intensity | % of heart rate reserve |
|---|---|
| Very light | < 30% |
| Light | 30–39% |
| Moderate | 40–59% |
| Vigorous | 60–89% |
| Near maximal | ≥ 90% |
Inputs explained
| Field | What to enter |
|---|---|
| Age | In years |
| Resting heart rate | In bpm |
| Maximum heart rate | Choose one: 220 − age (Fox), 208 − 0.7 × age (Tanaka), I know my maximum heart rate |
| Measured maximum heart rate | In bpm |
| Exercise intensity | In % |
What each result means
- Heart rate reserve = [Maximum heart rate] – [Resting heart rate]
- Target heart rate = [Resting heart rate] + [Exercise intensity]÷100×[Heart rate reserve]
- Moderate zone from (40%) = [Resting heart rate] + 0.4×[Heart rate reserve]
- Moderate zone to (59%) = [Resting heart rate] + 0.59×[Heart rate reserve]
- Vigorous zone from (60%) = [Resting heart rate] + 0.6×[Heart rate reserve]
- Vigorous zone to (89%) = [Resting heart rate] + 0.89×[Heart rate reserve]
Health note: this calculator is for education and screening only and is not a diagnosis or treatment advice. Discuss your results with a qualified clinician.
Formula
Max HR = 220 − age (or Tanaka: 208 − 0.7 × age, or your measured value)
Heart rate reserve (HRR) = max HR − resting HR
Target HR = resting HR + intensity × HRR
Worked example
Inputs — Age: 35 years; Resting heart rate: 65 bpm; Maximum heart rate: 220 − age (Fox); Exercise intensity: 70 %.
Results — Maximum heart rate = 185 bpm; Heart rate reserve = 120 bpm; Target heart rate = 149 bpm; Moderate zone from (40%) = 113 bpm; Moderate zone to (59%) = 136 bpm; Vigorous zone from (60%) = 137 bpm; Vigorous zone to (89%) = 172 bpm.
Key terms
- HRR
- Heart rate reserve: maximum minus resting heart rate.
Frequently asked questions
What is a normal resting heart rate?
60–100 bpm for adults; well-trained athletes can be in the 40s.
Is 220 − age accurate?
It can be off by 10–12 bpm either way. Tanaka's formula is slightly more accurate in older adults; a supervised test is best.
What intensity should I train at?
Most of your training at moderate intensity, with some vigorous work, is a good general plan.