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Target Heart Rate Calculator

Calculate exercise training heart rate zones using the Karvonen formula (heart rate reserve method). Personalize intensity targets based on your resting and maximum heart rates.

Reviewed by Christopher FloiedPublished Updated

This free online target heart rate calculator provides instant results with no signup required. All calculations run directly in your browser — your data is never sent to a server. Enter your values below and see results update in real time as you type. Perfect for everyday calculations, homework, or professional use.

Results

Heart Rate Reserve

120 bpm

Target HR (Low)

137 bpm

Target HR (High)

161 bpm

Zone 2 Low (60%)

137 bpm

Zone 2 High (70%)

149 bpm

How to Use This Calculator

1

Enter your input values

Fill in all required input fields for the Target Heart Rate Calculator. Most fields include unit selectors so you can work in your preferred unit system — metric or imperial, whichever matches your problem.

2

Review your inputs

Double-check that all values are correct and that you have selected the right units for each field. Incorrect units are the most common source of calculation errors and can produce results that are off by factors of 2, 10, or more.

3

Read the results

The Target Heart Rate Calculator instantly computes the output and displays results with units clearly labeled. All calculations happen in your browser — no loading time and no data sent to a server.

4

Explore parameter sensitivity

Try adjusting individual input values to see how the output changes. This is a quick and effective way to develop intuition about how different parameters influence the result and to identify which inputs have the largest effect.

When to Use This Calculator

  • •Use the Target Heart Rate Calculator for personal health tracking and wellness monitoring, establishing a baseline and tracking changes over time.
  • •Use it when recording fitness metrics to track progress toward health or athletic goals.
  • •Use it to compare measurements before and after a lifestyle, diet, or training change to quantify the impact.
  • •Use it as a conversation starter before a doctor's appointment, bringing objective data to discuss with a healthcare professional.

About Target Heart Rate Calculator

The Target Heart Rate Calculator uses the Karvonen formula (heart rate reserve method) to compute personalized training heart rate zones. Unlike the simpler percentage-of-max-HR method, the Karvonen formula accounts for your resting heart rate, providing more accurate intensity targets. Heart rate reserve (HRR) represents the difference between your maximum and resting heart rates — the usable range for exercise. A fitter individual with a lower resting heart rate has a larger HRR, which means more headroom for training adaptation. This calculator provides your custom target zone plus the popular Zone 2 range for aerobic base building.

The Math Behind It

The Karvonen formula was published by Finnish physiologist Martti Karvonen in 1957. It is more physiologically accurate than simply taking a percentage of HRmax because it accounts for individual fitness via resting heart rate. **Why HRR is superior to %HRmax**: At 60% HRmax, a sedentary person with a resting HR of 80 might be barely above rest, while a fit person with resting HR of 50 might be working moderately. The Karvonen formula adjusts for this by using the reserve range. **Training zones (Karvonen-based)**: - Zone 1 (50-60% HRR): Recovery, warm-up. Very light effort. - Zone 2 (60-70% HRR): Aerobic base. Can sustain for hours. Primary fat oxidation zone. This is where most training volume should occur. - Zone 3 (70-80% HRR): Tempo/moderate. Sustainable for 20-60 minutes. Mixed fuel (fat + glycogen). - Zone 4 (80-90% HRR): Threshold/hard. Lactate accumulation zone. Sustainable for 10-30 minutes. - Zone 5 (90-100% HRR): VO2max/anaerobic. Maximum effort. Sustainable for 1-5 minutes. **Zone 2 training** has gained significant attention for its role in metabolic health and longevity. At this intensity, fat oxidation is maximized, mitochondrial biogenesis is stimulated, and the aerobic system develops without excessive fatigue. Leading exercise physiologists recommend 80% of training volume in Zone 2 and 20% at high intensity (the polarized training model). **Measuring resting heart rate**: Take it first thing in the morning before getting out of bed, on 3 consecutive days, and average the results. A smartwatch or chest strap can automate this.

Formula Reference

Karvonen Formula

THR = (HRmax - HRrest) × Intensity% + HRrest

Variables: THR = target heart rate, HRR = heart rate reserve

Worked Examples

Example 1: Fit Individual

HRmax 185 bpm, resting HR 55 bpm, training at 60-80%

Step 1:HRR = 185 - 55 = 130 bpm
Step 2:Target low = 130 × 0.60 + 55 = 133 bpm
Step 3:Target high = 130 × 0.80 + 55 = 159 bpm
Step 4:Zone 2: 133-146 bpm

Train between 133-159 bpm for moderate-to-vigorous exercise. Zone 2 is 133-146 bpm.

Example 2: Sedentary Beginner

HRmax 180 bpm, resting HR 80 bpm, training at 50-65%

Step 1:HRR = 180 - 80 = 100 bpm
Step 2:Target low = 100 × 0.50 + 80 = 130 bpm
Step 3:Target high = 100 × 0.65 + 80 = 145 bpm

Start with 130-145 bpm for light-to-moderate exercise.

Common Mistakes & Tips

  • !Using a %HRmax calculator instead of Karvonen when resting HR is available. The Karvonen method is significantly more accurate for personalized zones.
  • !Not measuring true resting heart rate. Measure first thing in the morning, lying down, before coffee or stress.
  • !Training too intensely too often. Most training (80%) should be in Zone 2 for optimal adaptations.

Related Concepts

Max Heart Rate Calculator

Estimate HRmax using age-based formulas.

Cardiac Output Calculator

Heart rate is a direct component of cardiac output.

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Frequently Asked Questions

What is Zone 2 and why is it important?

Zone 2 (60-70% HRR) is the intensity at which fat oxidation is maximized and mitochondrial biogenesis is stimulated. You can sustain it for hours, talk in short sentences, and it builds your aerobic engine without excessive fatigue. Most endurance athletes spend 80% of training time here.

How do I know if my resting HR is accurate?

Measure it on 3 consecutive mornings immediately upon waking, before standing up. Average the three readings. A wearable device that tracks overnight HR provides even more reliable data. Do not measure after caffeine, alcohol, or poor sleep.

Does the Karvonen formula work for everyone?

It works well for most healthy adults. It is less reliable for individuals on beta-blockers (which blunt HR response), those with atrial fibrillation (irregular HR), or people with very high or low resting heart rates outside the normal 50-90 range.