Heart Rate Reserve Calculator
Karvonen zones from resting and max heart rate.
Enter your values
Enter the resting heart rate in bpm.
Enter the max heart rate in bpm.
Results update instantly as you type — no submit needed. Your values are remembered on this device, and the shareable link reopens the calculator with exactly these numbers.
- Heart rate reserve
- 130 bpm
- Zone 2 (aerobic base)
- 136-149 bpm
- Zone 4 (threshold)
- 162-175 bpm
- Zone 5 (VO2 max)
- 175-188 bpm
| Zone | Intensity | Range |
|---|---|---|
| 1 Recovery | 50-60% | 123-136 |
| 2 Aerobic | 60-70% | 136-149 |
| 3 Tempo | 70-80% | 149-162 |
| 4 Threshold | 80-90% | 162-175 |
| 5 Max | 90-100% | 175-188 |
Quick answer
Heart rate reserve is max minus resting heart rate; Karvonen zones apply an intensity percentage to that reserve.
target = resting + intensity x (max - resting)
At a glance
| What it does | Karvonen zones from resting and max heart rate. |
|---|---|
| Category | Fitness |
| Inputs needed | Resting heart rate, Max heart rate |
| Main output | Heart rate reserve |
| Formula | target = resting + intensity x (max - resting) |
| Cost | Free — no sign-up, no download |
How to use the Heart Rate Reserve Calculator
- 1Measure resting heart rate first thing in the morning for three days.
- 2Use a tested max heart rate if you have one, or 208 - 0.7 x age.
- 3Spend most training time in zone 2.
Inputs explained
- Resting heart rate(bpm)
- Enter the resting heart rate in bpm.
- Max heart rate(bpm)
- Enter the max heart rate in bpm.
Worked example
Using the values the calculator loads with:
Inputs
- Resting heart rate58 bpm
- Max heart rate188 bpm
Results
- Heart rate reserve130 bpm
- Zone 2 (aerobic base)136-149 bpm
- Zone 4 (threshold)162-175 bpm
- Zone 5 (VO2 max)175-188 bpm
Frequently asked questions
Why Karvonen over percent of max?
It accounts for your resting heart rate, giving zones that fit your fitness, not an average.
How do I find true max?
A supervised ramp test or an all-out hill effort at the end of a hard session.
What do I need to enter into the Heart Rate Reserve Calculator?
Just 2 values: resting heart rate, max heart rate. Every field starts with a realistic example, so you can change one number at a time and watch the result update instantly.
How does the Heart Rate Reserve Calculator work out the answer?
Heart rate reserve is max minus resting heart rate; Karvonen zones apply an intensity percentage to that reserve. It applies the formula target = resting + intensity x (max - resting) and shows the working so you can check each step by hand.
Is the Heart Rate Reserve Calculator free, and do I need an account?
It is completely free with no sign-up, no download and no usage limit. Everything is calculated in your browser, so the numbers you type never leave your device.
Results are estimates for general information. For medical, legal, structural or financial decisions, confirm with a qualified professional.