Inputs
Example Data
| Scenario | Age | Rest HR | Intensity | Duration | MET | Estimated target HR |
|---|---|---|---|---|---|---|
| Brisk walking | 35 | 62 | 60% (HRR) | 40 min | 4.3 | ~140 bpm |
| Tempo run | 28 | 55 | 80% (HRR) | 25 min | 10.0 | ~176 bpm |
| Easy cycling | 45 | 65 | 55% (HRmax) | 60 min | 6.8 | ~92 bpm |
Formulas Used
- Maximum Heart Rate (HRmax): Tanaka: HRmax = 208 - 0.7xage, or Fox: HRmax = 220 - age, or a custom value.
- Heart Rate Reserve (HRR): HRR = HRmax - RestHR.
- Target Heart Rate (Karvonen): TargetHR = RestHR + HRR x intensity, where intensity is a decimal (e.g., 0.70).
- Target Heart Rate (%HRmax): TargetHR = HRmax x intensity.
- Calories (MET method): kcal/min = MET x 3.5 x weight(kg) / 200, then kcal = kcal/min x minutes.
How to Use This Calculator
- Enter your age and a measured resting heart rate.
- Choose an HRmax method, or set a custom HRmax.
- Pick an intensity percentage and a mode (HRR or %HRmax).
- Add weight, duration, and a MET value to estimate calories.
- Press Calculate to see results above the form.
- Use the download buttons to export your report.
Why intensity targets reduce guesswork
Heart rate and workload rarely match perfectly day to day. Using an intensity target helps you repeat sessions with similar physiological stress. A 10 bpm drift can move a workout from aerobic support toward threshold fatigue, especially when duration exceeds 30 minutes.
Heart rate reserve improves personalization
Two people can share the same estimated maximum heart rate but differ by 20 bpm in resting heart rate. Heart rate reserve adjusts for that gap. For example, with HRmax 190 and RestHR 60, HRR is 130. Training at 70% HRR targets about 151 bpm, not the 133 bpm you get from 70% HRmax.
Zone structure supports progressive overload
Zone 1 to Zone 2 builds volume and technique, Zone 3 develops sustainable pace, and Zones 4 to 5 are best reserved for shorter intervals. Keeping easy days truly easy can preserve quality on hard days and reduce recovery time by 24 to 48 hours for many athletes.
MET-based calories provide workload context
Calorie estimates are useful for planning fuel and weekly workload. Using the MET equation, a 70 kg person at 8.0 METs burns about 9.8 kcal per minute. Over a 45-minute session, that is roughly 441 kcal, before considering efficiency and terrain.
RPE validates the numbers in real conditions
Perceived effort is a safety check. Heat, dehydration, caffeine, and lack of sleep can elevate heart rate for the same pace. If RPE is high while heart rate is low, muscular fatigue may be limiting. If RPE is low and heart rate is high, you may be overreaching or stressed.
Practical weekly application
A balanced week often includes 2 to 4 sessions in Zone 2, one moderate progression in Zone 3, and 1 interval session touching Zone 4. Use the target heart rate to hold steady, then review your exported report to compare planned intensity versus actual feeling and calories. Add a short warmup in Zone 1 before demanding work, and cool down until breathing normalizes. When setting goals, increase duration or intensity, not both in the same week. For beginners, stay near the lower bound of each zone and re-test resting heart rate every two weeks. Consistency matters more than perfection across single sessions.
FAQs
Which HRmax method should I choose?
Use Tanaka for many adults, Fox for quick estimates, or Custom if you have a tested maximum. Pick one method and stay consistent for comparisons.
Is heart rate reserve better than percent of HRmax?
HRR accounts for resting heart rate differences, so targets can feel more individualized. Percent of HRmax is simpler and still useful for broad training guidance.
Why does my heart rate drift upward during steady exercise?
Cardiac drift can rise with heat, dehydration, or fatigue, even at the same pace. Use hydration, cooler conditions, and RPE to keep effort appropriate.
How do I pick a MET value?
Choose a MET close to your activity’s intensity. Walking is often 3–5 METs, easy jogging 6–8, and vigorous cycling 8–12. Your terrain and fitness can shift values.
Can medication affect these results?
Yes. Beta blockers and some stimulants can change heart rate response. In those cases, rely more on RPE, talk test, and professional advice for safe targets.
How often should I update resting heart rate?
Measure for several mornings and use an average. Recheck every 2–4 weeks or after a major training change, illness, or travel that affects sleep.