liminfoHeart Rate Zone Calculator
Free web tool: Heart Rate Zone Calculator
Zone 1 - Very Light
Warm-up, recovery | 50%-60% intensity
125 - 138
bpm
Zone 2 - Light
Fat burning, base fitness | 60%-70% intensity
138 - 151
bpm
Zone 3 - Moderate
Aerobic endurance | 70%-80% intensity
151 - 164
bpm
Zone 4 - Hard
Anaerobic threshold | 80%-90% intensity
164 - 177
bpm
Zone 5 - Maximum
Maximum effort, speed | 90%-100% intensity
177 - 190
bpm
About Heart Rate Zone Calculator
The Heart Rate Zone Calculator determines your five personalized training zones in beats per minute (bpm), based on your age and resting heart rate. It supports two calculation methods: the Karvonen formula, which accounts for your heart rate reserve (HRR = max HR minus resting HR) to produce individualized targets, and the simple %MHR method, which calculates zones as a direct percentage of your maximum heart rate (estimated as 220 minus age). Both methods divide training intensity into five zones: Zone 1 (50–60%, very light, warm-up and recovery), Zone 2 (60–70%, fat burning and base fitness), Zone 3 (70–80%, aerobic endurance), Zone 4 (80–90%, anaerobic threshold), and Zone 5 (90–100%, maximum effort and speed).
This calculator is widely used by recreational runners, cyclists, swimmers, personal trainers, and competitive athletes who want to train at the correct physiological intensity. Training below Zone 2 builds aerobic base without fatigue accumulation; Zone 3 and 4 improve lactate threshold and cardiovascular capacity; Zone 5 is reserved for short sprint intervals. Knowing your exact bpm targets prevents both under-training and overtraining, which is a common cause of injury and burnout.
The tool automatically computes the maximum heart rate and heart rate reserve as secondary outputs, giving you full context alongside the zone table. All calculations are performed in real time within your browser using standard physiological formulas — no account is required and no health data is stored or transmitted. The interface is fully responsive and supports dark mode for gym use or low-light environments.
Key Features
- Five training zones with bpm ranges calculated in real time as you type
- Karvonen formula using heart rate reserve for personalized, individualized targets
- Simple %MHR method for a quick baseline estimate without resting HR measurement
- Displays maximum heart rate (220 - age) and HR reserve as reference values
- Color-coded zone cards from gray (recovery) to red (maximum effort) for at-a-glance reading
- Each zone shows intensity percentage range and a plain-language purpose description
- Instant switching between Karvonen and simple %MHR methods to compare results
- Fully private — no health data leaves your browser, no account or login required
Frequently Asked Questions
What is the Karvonen formula for heart rate zones?
The Karvonen formula calculates target heart rate as: resting HR + (heart rate reserve × zone percentage). Heart rate reserve (HRR) is your maximum HR minus your resting HR. This method produces more personalized targets than the simple %MHR method because it accounts for your individual fitness baseline.
What is the difference between Karvonen and simple %MHR?
Simple %MHR multiplies your maximum heart rate (220 - age) by the zone percentage directly. Karvonen instead works on the range between your resting HR and max HR. For a fit person with a low resting HR, the Karvonen formula gives higher zone targets; for someone less fit, targets will be lower than the simple method.
How is maximum heart rate estimated?
Maximum heart rate is estimated using the standard age-based formula: 220 minus your age. This is an average and individual actual max HR can differ by ±10–20 bpm. For the most accurate zones, you would need a graded exercise test or all-out effort interval to measure your true max HR.
What is Zone 2 training and why is it popular?
Zone 2 training (60–70% of max HR) is the fat-burning aerobic base zone. At this intensity, the body primarily uses fat as fuel, mitochondrial density increases, and lactate stays low. It is recommended for endurance base building and is popular in training plans because it enables high training volume without excessive recovery time.
What is the anaerobic threshold in Zone 4?
Zone 4 (80–90% of max HR) is where lactate production starts to outpace clearance, causing the burning sensation in muscles. Training in this zone improves your lactate threshold — the speed or intensity you can sustain before fatigue accumulates. Athletes use threshold intervals to raise their sustainable race pace.
Why does my resting heart rate affect my training zones with the Karvonen method?
A lower resting HR means a larger heart rate reserve, so each Karvonen zone corresponds to higher absolute bpm values. A well-trained endurance athlete with a resting HR of 40 bpm will have higher zone targets than a sedentary person with a resting HR of 75 bpm — even if both are the same age.
What resting heart rate should I enter?
Measure your resting heart rate in the morning before getting out of bed, ideally after several minutes of lying still. A typical resting HR is 60–80 bpm for adults. Athletes commonly have resting HR in the 40–60 bpm range. An accurate resting HR measurement is essential for the Karvonen formula to be meaningful.
Can this calculator be used for cycling, swimming, or rowing?
Yes. Heart rate zones are sport-agnostic in principle, though true max HR can differ by sport. Cycling max HR is often 5–10 bpm lower than running max HR due to reduced muscle mass recruitment. If precision is important, use sport-specific max HR measurements rather than the generic 220 - age formula.