Karvonen Formula Calculator
Calculate your personalized target heart rate for cardio training. The Karvonen formula uses your resting heart rate to determine precise training zones.
Measure first thing in the morning before getting out of bed for best accuracy
🎯 Target Heart Rate at 70% Intensity
Complete Training Zones
| Zone | Intensity | Heart Rate Range | Purpose |
|---|---|---|---|
| Zone 1 | 50–60% | -- – -- bpm | Recovery, warm-up |
| Zone 2 | 60–70% | -- – -- bpm | Aerobic base, fat burning |
| Zone 3 | 70–80% | -- – -- bpm | Aerobic endurance |
| Zone 4 | 80–90% | -- – -- bpm | Lactate threshold |
| Zone 5 | 90–100% | -- – -- bpm | Maximum effort |
Understanding the Karvonen Formula
The Karvonen formula (also called Heart Rate Reserve method) is more personalized than simple percentage methods because it accounts for your resting heart rate, which reflects your fitness level.
The Formulas
Age: 35 years, Resting HR: 65 bpm, Target intensity: 70%
Step 1: HRmax = 220 − 35 = 185 bpm
Step 2: HRR = 185 − 65 = 120 bpm
Step 3: Target HR = (120 × 0.70) + 65 = 84 + 65 = 149 bpm
At 70% intensity, this person should aim for approximately 149 bpm during exercise.
How to Measure Resting Heart Rate
- Measure in the morning: Check your pulse before getting out of bed, after a restful night's sleep.
- Find your pulse: Place two fingers on your wrist (radial artery) or neck (carotid artery).
- Count for 60 seconds: Count the beats for a full minute, or 30 seconds and multiply by 2.
- Take multiple readings: Measure on 3-5 consecutive days and average the results.
- Avoid stimulants: Caffeine, stress, and illness can elevate resting heart rate.
Why Resting Heart Rate Matters
Lower resting heart rate generally indicates better cardiovascular fitness. Elite endurance athletes may have RHR as low as 40-50 bpm, while sedentary adults typically range from 60-80 bpm. As you get fitter, your RHR decreases, and the Karvonen formula automatically adjusts your training zones.
Frequently Asked Questions
The Karvonen formula calculates target heart rate using Heart Rate Reserve (HRR)—the difference between maximum and resting heart rate. It's more personalized than simple percentage methods because it accounts for individual fitness levels through resting heart rate.
The 220-age formula is a rough estimate with significant individual variation (±10-12 bpm). The Tanaka formula (208 − 0.7×age) may be more accurate. For precision, a graded exercise test can determine your true HRmax.
For adults, 60-100 bpm is considered normal, though fit individuals often have RHR of 40-60 bpm. Elite endurance athletes may have RHR below 40 bpm. Generally, lower RHR indicates better cardiovascular fitness.
It depends on your goals. Zone 2 (60-70%) builds aerobic base and burns fat. Zone 3 (70-80%) improves endurance. Zone 4 (80-90%) increases lactate threshold. Most training plans mix zones with emphasis on Zone 2.
Zone 2 training builds aerobic capacity efficiently without excessive fatigue. It improves mitochondrial function, fat oxidation, and endurance. Many elite athletes spend 80% of training time in Zone 2.
Simple percentage methods (e.g., 70% of HRmax) don't account for fitness level. Two people with the same HRmax but different resting HRs would get the same target—but they're at different fitness levels. Karvonen adjusts for this.
Yes, beta-blockers and some other medications lower heart rate. Standard formulas may not apply. Consult your doctor for modified target zones or consider using Rate of Perceived Exertion (RPE) instead.
First thing in the morning, before getting out of bed, after a restful sleep. Avoid measuring after caffeine, stress, or illness. Take measurements over several days and average them.
HRR is the difference between your maximum and resting heart rate. It represents your "working range"—the span of heart rates available for exercise. A larger HRR often indicates better fitness.
Yes, the Karvonen formula applies to running, cycling, swimming, rowing, and other cardio activities. Heart rate response may vary slightly by activity (e.g., swimming typically shows lower HR), but the zones remain useful.