Maximum Heart Rate (Common Formula)
The most widely used estimate of maximum heart rate. Simple and quick but has a standard deviation of about ±12 bpm. Alternative formulas (Inbar, Londeree, Miller) may be more accurate for specific populations.
HR_max = 220 − age
Heart Rate Reserve
Heart rate reserve is the difference between your maximum and resting heart rates. It represents your usable training range and is the foundation of the Karvonen method for setting target heart rate zones.
HR_reserve = HR_max − HR_rest
Target Heart Rate (Karvonen Method)
The Karvonen method uses heart rate reserve to set personalized target zones for each exercise intensity. It accounts for resting heart rate, giving more accurate zones than simple percentage of max HR.
THR = (HR_max − HR_rest) × intensity + HR_rest
How It Works
This calculator estimates three key heart-rate metrics. Maximum heart rate (HR_max) is the fastest your heart can beat during all-out effort. Heart rate reserve is the difference between max and resting rates, representing your usable training range. The Karvonen method then uses that reserve to set personalized target zones for each exercise intensity.
Example Problem
A 30-year-old with a resting heart rate of 65 bpm wants to find their 70% Karvonen target.
- Max HR (common): 220 − 30 = 190 bpm
- HR reserve: 190 − 65 = 125 bpm
- Target HR at 70%: (125 × 0.70) + 65 = 152.5 bpm
When to Use Each Variable
- Solve for Max HR (Common) — when you need a quick estimate using 220 minus age, e.g., setting up a basic training zone chart.
- Solve for Max HR (Inbar) — when you want a research-based alternative formula, e.g., comparing estimates for older or highly fit populations.
- Solve for HR Reserve — when you know your max and resting heart rates, e.g., finding the range available for training intensity.
- Solve for Target HR (Karvonen) — when you want personalized training zones that account for resting heart rate, e.g., setting a 70% intensity target for aerobic training.
Key Concepts
Maximum heart rate is the fastest your heart can beat during all-out exertion and decreases with age. Heart rate reserve (HRR) is the difference between max and resting heart rates — it represents the usable training range. The Karvonen method multiplies HRR by a target intensity percentage and adds back the resting heart rate, producing more personalized zones than simple percentage-of-max methods.
Applications
- Endurance training: setting target heart rate zones for aerobic base building, tempo runs, and interval workouts
- Cardiac rehabilitation: prescribing safe exercise intensities for patients recovering from heart events
- Fitness assessment: using resting heart rate trends to track cardiovascular fitness improvements over time
- Wearable technology: calibrating heart rate monitors and smartwatches for accurate zone alerts
Common Mistakes
- Treating 220 minus age as exact — it has a standard deviation of ±12 bpm and may be off significantly for individuals
- Using simple percentage of max HR instead of the Karvonen method — simple percentage ignores resting heart rate and underestimates actual intensity
- Not measuring resting heart rate correctly — it should be taken first thing in the morning before getting out of bed
- Applying the same max HR formula to all populations — older adults, women, and highly trained athletes may benefit from alternative formulas like Inbar or Londeree
Frequently Asked Questions
How accurate is the 220 minus age formula?
The 220 minus age formula is a rough estimate with a standard deviation of about ±12 bpm. Alternative formulas (Inbar, Londeree, Miller) may be more accurate for specific populations, but a clinical stress test is the only precise way to measure max HR.
What is a good resting heart rate?
A normal resting heart rate for adults is 60–100 bpm. Well-trained athletes may have resting rates as low as 40–50 bpm. A lower resting rate generally indicates better cardiovascular fitness.
What heart rate zone burns the most fat?
The "fat-burning zone" is roughly 60–70% of max HR. While a higher percentage of calories come from fat at lower intensities, higher-intensity exercise burns more total calories and fat overall per session.
Why use the Karvonen method instead of simple percentage?
The Karvonen method accounts for resting heart rate, giving a more personalized zone. Two people with the same max HR but different resting rates will get different target zones, reflecting their individual fitness levels.
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