Target Heart Rate Calculator (5 training zones)
Enter your age and resting heart rate. The calculator returns max heart rate (220 โ age), heart rate reserve, and the 5 standard training zones. Toggle Karvonen for personalized zones based on your fitness level.
- Max heart rate
- 190
- Heart rate reserve
- 130
Training zones
- Zone 1: Recovery (50-60%)Warm-up, cool-down, rest day light activity.125โ138 bpm
- Zone 2: Fat burn (60-70%)Long endurance, fat oxidation, base building.138โ151 bpm
- Zone 3: Aerobic (70-80%)Improves aerobic capacity, all-day workhorse.151โ164 bpm
- Zone 4: Threshold (80-90%)Lactate threshold work, race pace.164โ177 bpm
- Zone 5: Max (90-100%)VOโmax intervals, sprints, near maximum effort.177โ190 bpm
How it works
Two formulas, two levels of accuracy
Simple percentage of MHR: zone = max_hr ร percent. Easy to compute mentally; the standard '220 โ age' max-HR estimate has a ยฑ10-12 bpm error so zones derived from it are approximate.
Karvonen formula: zone = resting_hr + (max_hr โ resting_hr) ร percent. Accounts for your individual resting heart rate, a proxy for fitness level. A fit person with a 50 bpm resting HR will have lower-numbered zones than an unfit person at the same age and percentage. More accurate for personalized training; the default in our calculator.
What each zone is for
Zone 1 (50-60%): Recovery. Active rest, easy walking. Heart rate returns toward baseline.
Zone 2 (60-70%): The 'fat burn' zone. Maximum reliance on fat as fuel. Long, steady-state cardio. The most popular zone for endurance athletes building a base.
Zone 3 (70-80%): Aerobic. Improves cardiovascular efficiency. Conversational pace; you can talk in short sentences but not in long ones.
Zone 4 (80-90%): Threshold. Pushing the lactate threshold. Race pace for 5K-10K runners. Hard but sustainable for 20-60 minutes.
Zone 5 (90-100%): Max effort. Used in interval training (e.g., 30 seconds hard, 90 seconds rest). Improves VOโmax and top-end speed.
How to actually measure heart rate
Wrist-based monitors (Apple Watch, Garmin, Fitbit) are accurate within ยฑ5 bpm for steady-state cardio. Less accurate for high-intensity intervals or wrist movement (rowing, weight training).
Chest straps (Polar H10, Wahoo TICKR) are gold standard โ used in research, accurate to ยฑ1-2 bpm. Worth the investment for serious training.
Manual count: take your pulse for 15 seconds and multiply by 4. Useful for spot-checking but impractical during high intensity. Use first thing in the morning before getting out of bed for resting HR.
Frequently asked questions
โบIs '220 โ age' accurate?
It's a population average with about ยฑ10-12 bpm individual variation. For better accuracy, do a max-HR test (run a hard 5-minute hill, last minute all-out) or get a stress test under medical supervision.
โบWhat's a normal resting heart rate?
Adults: 60-100 bpm. Athletes often 40-60 bpm. Below 40 may indicate excellent conditioning OR a medical condition (bradycardia) โ see a doctor if you have symptoms.
โบWhen should I be in zone 2?
Most aerobic base training. 80% of weekly cardio time at zone 2 is a common endurance training principle (the '80/20 rule'). Maximizes fat oxidation and cardiovascular adaptations.
โบWhy does my watch say a different max HR?
Modern smartwatches estimate max HR by observing your highest readings. They learn from your real efforts, so they're typically more accurate than '220 โ age'. Trust your watch's number if you've done max efforts.
โบCan I skip zones in training?
You can, but balanced training has all zones in some ratio. Pure zone 5 sprints with no zone 2 base leads to plateau and burnout. Pure zone 2 with no high intensity caps your top-end fitness.
โบWhat if my resting HR is unusually low?
Athletes often have 40-50 bpm resting HR. Karvonen handles this correctly โ your zones will be lower in absolute bpm but the same percentage of HRR. If <40 bpm and you have dizziness/fainting, see a doctor.
โบDo these zones apply to swimming and cycling?
The percentages are the same, but max HR varies by mode: cycling typically 5-10 bpm lower than running, swimming 10-15 bpm lower. Test max in each mode for accurate sport-specific zones.
โบDoes the data leave my browser?
No. Calculation runs locally; nothing is sent to a server.
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