Heart Rate Zone Calculator
Calculate your personalised target heart rate zones for optimal training using both max HR and heart rate reserve methods.
What are heart rate zones?
Heart rate zones are ranges of exercise intensity expressed as a percentage of your maximum heart rate (MHR). Each zone corresponds to a distinct physiological state — different fuel sources are burned, different cardiovascular adaptations occur, and different muscle fibre types are recruited. Training deliberately across zones is one of the most effective ways to improve endurance, speed, and overall fitness.
Most coaches and sports scientists use a five-zone model, though some systems use three or six zones. This calculator uses the widely accepted five-zone model with two methods: percentage of maximum heart rate (% MHR) and the Karvonen heart rate reserve method, which accounts for your resting heart rate and is more accurate for individuals with high cardiorespiratory fitness.
How maximum heart rate is estimated
The most common formula is:
Max Heart Rate (MHR) = 220 − ageThis formula is simple and population-level accurate, but individual MHR can vary by ±10–20 bpm from the estimate. More accurate formulas have been proposed:
| Formula | Equation | Notes |
|---|---|---|
| Fox (1971) | 220 − age | Most widely used; least accurate for fit individuals |
| Tanaka et al. (2001) | 208 − 0.7 × age | More accurate across all ages; validated in large study |
| Gelish et al. (2007) | 207 − 0.7 × age | Similar to Tanaka; slightly lower at younger ages |
| Inbar et al. (1994) | 205.8 − 0.685 × age | Accurate for highly trained athletes |
The Karvonen method (heart rate reserve)
The Karvonen formula, developed by Finnish physiologist Martti Karvonen in 1957, accounts for resting heart rate by using your heart rate reserve (HRR) — the difference between maximum and resting heart rate. It produces training zones that are more personalised, particularly for individuals with a low resting heart rate (fit athletes typically have resting rates of 40–55 bpm).
Heart Rate Reserve (HRR) = MHR − Resting HR
Target HR = Resting HR + (HRR × zone percentage)For example, a 35-year-old with an MHR of 185 bpm and a resting rate of 50 bpm has an HRR of 135 bpm. Their Zone 2 target (60–70%) using Karvonen would be 131–145 bpm, compared to 111–130 bpm using simple % MHR. Karvonen zones are generally higher and better reflect actual exertion for fit individuals.
What each zone achieves
Zone 1 (50–60%): Active recovery
Blood flow increases gently, clearing metabolic waste from muscles without creating additional fatigue. This is the zone used for warm-up, cool-down, and easy recovery days between hard sessions. Even at this low intensity, Zone 1 training improves baseline aerobic capacity over time.
Zone 2 (60–70%): Aerobic base and fat burn
Zone 2 is the foundation of all endurance training. At this intensity, the body relies primarily on fat as fuel — oxygen delivery is high enough to sustain aerobic metabolism. Top-tier endurance athletes (marathon runners, cyclists, triathletes) spend 70–80% of their total training volume in Zone 2. It stimulates mitochondrial growth in muscle cells and improves the capacity to clear lactate, effectively raising your threshold pace.
Zone 3 (70–80%): Aerobic threshold / tempo
Often called "comfortably hard," Zone 3 is the pace you might hold for a 60-minute race effort. It develops cardiovascular efficiency and improves your lactate threshold — the point at which lactate begins accumulating faster than it can be cleared. Too much Zone 3 work, however, can leave athletes in a "grey zone" that causes cumulative fatigue without the specific adaptations of Zones 2 or 4.
Zone 4 (80–90%): Lactate threshold / race pace
Training in Zone 4 pushes your lactate threshold upward, meaning you can sustain a faster pace before fatigue sets in. This is approximately 10 km to half-marathon race pace for runners. Sessions are typically 20–40 minutes of sustained effort, or intervals of 8–12 minutes. VO₂max (the maximum rate of oxygen consumption) also improves significantly at this intensity.
Zone 5 (90–100%): VO₂max and anaerobic capacity
Zone 5 training is performed in short, intense bursts — think 30-second to 2-minute all-out efforts. It maximises VO₂max and develops anaerobic power and speed. Because it is extremely demanding on the nervous system and muscles, Zone 5 should constitute a small proportion of total training volume (typically 5–10%) and requires adequate recovery between sessions.
Recommended training distribution
Research on elite endurance athletes consistently shows a polarised training distribution: 75–80% of sessions in low intensity (Zones 1–2), and 15–20% in high intensity (Zones 4–5), with relatively little time in the moderate Zone 3. This approach, sometimes called the "80/20 rule," produces better outcomes than spending most time in the grey zone.
| Training goal | Zone 1–2 | Zone 3 | Zone 4–5 |
|---|---|---|---|
| General fitness / health | 70% | 20% | 10% |
| Endurance (5K–marathon) | 80% | 5% | 15% |
| Cycling (road/triathlon) | 75% | 5% | 20% |
| Weight loss focus | 60% | 25% | 15% |
| Beginner (first 3 months) | 90% | 10% | 0% |
How to measure your heart rate accurately
- Chest strap: Most accurate wearable option. Measures electrical signals directly from the heart. Recommended for interval training.
- Optical wrist sensor (smartwatch): Convenient and accurate at steady-state intensities, but can lag during rapid changes in effort (e.g., sprint intervals).
- Manual palpation: Place two fingers on your carotid artery (neck) or radial artery (wrist), count beats for 15 seconds, multiply by 4. Less practical during exercise.
- Fingertip pulse oximeters: Accurate at rest; unreliable during movement.
Frequently asked questions
My heart rate is always higher than the zone targets — is that a problem?
Heart rates vary significantly between individuals. Age-predicted MHR (220 − age) has a standard deviation of about 10–12 bpm, meaning it is quite common for your actual MHR to be higher or lower. If you feel fine and can pass the "talk test" (able to speak in short sentences at Zone 2 pace), your zones are appropriate regardless of the number.
Does heart rate training apply to strength training?
Heart rate zones are primarily developed for steady-state aerobic exercise. During weight training, heart rate spikes rapidly and may not reflect metabolic intensity in the same way. Rating of perceived exertion (RPE) is generally more useful for resistance training.
What is cardiac drift and why does it matter?
Cardiac drift is the gradual rise in heart rate during prolonged exercise at constant pace, caused by dehydration and heat. Your heart rate may drift into Zone 3 or 4 during a long Zone 2 run — in this case, slow your pace rather than forcing yourself into a higher zone. It is a sign you need to drink more.
How long should each zone workout be?
Zone 1: 20–60 minutes (recovery). Zone 2: 45–180 minutes (base building). Zone 3: 20–60 minutes (tempo). Zone 4: 20–40 minutes continuous or 4–8 × 6–12 min intervals. Zone 5: 5–20 minutes total (short intervals of 30 sec–2 min).
Max Heart Rate = 220 − age Zones are percentages of max HR, each targeting different physiological adaptations. Heart Rate Reserve method (Karvonen) factors in resting heart rate for greater accuracy.