Heart Rate Calculator
Calculate your maximum heart rate and personalized training zones using either the standard formula or the Karvonen method.
Maximum Heart Rate
| Zone | Intensity | Target BPM |
|---|---|---|
| Light / Fat Burn | 50–60% | 93–111 bpm |
| Moderate / Cardio | 60–70% | 111–130 bpm |
| Aerobic / Endurance | 70–80% | 130–148 bpm |
| Hard / Anaerobic | 80–90% | 148–167 bpm |
| Maximum Effort | 90–100% | 167–185 bpm |
Your max heart rate sets the ceiling for every training zone you’ll ever use. Get it wrong and your Zone 2 run is actually Zone 3, your intervals aren’t hard enough, and your fat-burning sessions sit in the wrong range entirely.
This heart rate calculator finds your maximum heart rate by age, splits it into five training zones, and shows your Zone 2, fat-burning, and peak aerobic targets — all from one tool. Below, you’ll also find the formulas so you can check the numbers yourself.
How to calculate max heart rate
Your maximum heart rate is the highest number of times your heart can beat per minute during all-out effort. It’s determined mostly by age and genetics — not fitness level. Even elite athletes have the same max heart rate formula applied to them as beginners.
The standard formula is 220 minus your age. A 35-year-old has an estimated max heart rate of 185 bpm. That figure becomes the anchor for every zone calculation below.
The three max heart rate formulas
| Formula | Equation | Best for |
|---|---|---|
| Fox (1971) | 220 − age | General population, quick estimates |
| Tanaka (2001) | 208 − (0.7 × age) | Adults over 40, more accurate at higher ages |
| Gulati (2010) | 206 − (0.88 × age) | Women specifically |
The Fox formula is the most widely used because it’s simple. Research published in the Journal of the American College of Cardiology found the Tanaka formula reduces prediction error by roughly 30% in people over 40, which is worth knowing if you’re training seriously past that age. Australian fitness professionals commonly use both.
To calculate manually: take 220, subtract your age, done. For a 45-year-old, that’s 220 − 45 = 175 bpm.
Heart rate zones: the complete 5-zone breakdown
Heart rate zones divide your training intensity into five bands, each triggering a different physiological response. Every zone is expressed as a percentage of your maximum heart rate.
| Zone | Name | % of Max HR | What happens |
|---|---|---|---|
| Zone 1 | Very light | 50–60% | Active recovery, warm-up, cool-down |
| Zone 2 | Light / fat burning | 60–70% | Aerobic base building, fat metabolism |
| Zone 3 | Moderate / aerobic | 70–80% | Cardiovascular fitness, sustained effort |
| Zone 4 | Hard / threshold | 80–90% | Lactate threshold, race pace |
| Zone 5 | Maximum | 90–100% | Sprint, VO2 max intervals, short bursts |
For a 35-year-old with a max HR of 185 bpm:
- Zone 2 sits at 111–130 bpm
- Zone 4 sits at 148–167 bpm
Most training programs target Zone 2 (70–80% of total training volume) and Zone 4 (10–20%). Zone 5 work is high-reward but requires full recovery between sessions.
How to calculate your training heart rate zones
Multiply your max heart rate by the lower and upper percentages for each zone.
Example — 40-year-old, max HR = 180 bpm:
- Zone 1: 180 × 0.50 = 90 bpm → 180 × 0.60 = 108 bpm → 90–108 bpm
- Zone 2: 180 × 0.60 = 108 bpm → 180 × 0.70 = 126 bpm → 108–126 bpm
- Zone 3: 180 × 0.70 = 126 bpm → 180 × 0.80 = 144 bpm → 126–144 bpm
- Zone 4: 180 × 0.80 = 144 bpm → 180 × 0.90 = 162 bpm → 144–162 bpm
- Zone 5: 180 × 0.90 = 162 bpm → 180 × 1.00 = 180 bpm → 162–180 bpm
Zone 2 heart rate: why it matters and how to calculate it
Zone 2 training — sometimes called low-intensity steady-state cardio — has become one of the most discussed training methods among endurance athletes and general fitness audiences alike. It’s the zone where your body primarily burns fat as fuel and builds mitochondrial density.
Zone 2 is 60–70% of your maximum heart rate.
To calculate your Zone 2 range:
- Lower bound: max HR × 0.60
- Upper bound: max HR × 0.70
For a 30-year-old (max HR = 190 bpm): Zone 2 = 114–133 bpm.
The key marker for Zone 2 is the ability to hold a full conversation. If you’re struggling to speak in full sentences, you’ve moved into Zone 3. If talking feels completely effortless, you’re in Zone 1.
The Karvonen formula — a more precise method
The Karvonen formula accounts for your resting heart rate, which makes zone calculations more accurate for people with a lower resting HR (common in trained athletes).
Karvonen target HR = ((Max HR − Resting HR) × % intensity) + Resting HR
Example: 35-year-old, max HR 185 bpm, resting HR 55 bpm, targeting 65% intensity (mid-Zone 2):
((185 − 55) × 0.65) + 55 = (130 × 0.65) + 55 = 84.5 + 55 = 139.5 bpm
Compare that to the simple method: 185 × 0.65 = 120 bpm. A meaningful difference for a trained athlete.
How to calculate heart rate from an ECG
An ECG (electrocardiogram) records the electrical activity of your heart on a graph. Calculating heart rate from an ECG is a clinical skill, but the method is straightforward.
The large-square method (most common)
Each large square on an ECG represents 0.2 seconds at standard paper speed (25 mm/s). The formula is:
Heart rate = 300 ÷ number of large squares between two R waves
The R wave is the tall spike on each cardiac cycle. Count the number of large squares from one R peak to the next, then divide 300 by that number.
| Large squares between R waves | Heart rate |
|---|---|
| 1 | 300 bpm |
| 2 | 150 bpm |
| 3 | 100 bpm |
| 4 | 75 bpm |
| 5 | 60 bpm |
| 6 | 50 bpm |
A quick memory trick used in clinical settings: “300, 150, 100, 75, 60, 50” — memorise this sequence and you can estimate any regular rhythm at a glance.
The small-square method (more precise)
Each small square = 0.04 seconds. For a more accurate calculation:
Heart rate = 1,500 ÷ number of small squares between two R waves
Calculating heart rate on an irregular ECG
Neither method above works for irregular rhythms like atrial fibrillation. Instead, count the number of QRS complexes across a 10-second strip and multiply by 6.
Heart rate = QRS complexes in 10 seconds × 6
This gives the average rate over a full minute. It’s the standard method for irregular rhythms used in Australian clinical practice.
Fat-burning heart rate zone: what it is and how to find it
The fat-burning zone sits inside Zone 2 — typically 60–70% of your max heart rate. At this intensity, fat provides the majority of your fuel source, with carbohydrates contributing less. This doesn’t mean you burn more total calories here, but a higher proportion comes from stored fat.
Fat-burning heart rate = max HR × 0.60 to 0.70
For a 50-year-old (max HR = 170 bpm): fat-burning zone = 102–119 bpm.
The term “fat-burning zone” can be misleading. You burn more total fat calories at higher intensities (because total energy expenditure is higher) but a lower percentage from fat. Zone 2 training matters for fat metabolism because it trains your body to oxidise fat more efficiently — a benefit that compounds over time.
How to calculate your fat-burning heart rate without a calculator
- Find your max HR: 220 − your age
- Multiply by 0.60 for the lower bound
- Multiply by 0.70 for the upper bound
That range is your fat-burning zone.
Resting heart rate: what it means and how to measure it
Your resting heart rate is the number of times your heart beats per minute when you’re completely at rest. A normal range for adults is 60–100 bpm. Well-trained athletes often measure 40–60 bpm.
To measure manually: sit quietly for 5 minutes, then count heartbeats over 60 seconds (or count for 15 seconds and multiply by 4). The most accurate reading is right after waking, before getting out of bed.
Resting heart rate matters for the Karvonen formula above and as a long-term fitness indicator. A decrease of 5–10 bpm over several months of training is a reliable sign your aerobic fitness is improving.
Using a heart rate monitor vs. manual calculation
Most Australians training with a heart rate monitor — Garmin, Polar, Apple Watch, Wahoo — use the same 220-minus-age formula in the background. The difference is that wrist-based optical sensors can drift by 5–15 bpm during high-intensity efforts.
A chest strap monitor (Garmin HRM-Pro, Polar H10) measures electrical signals directly, the same principle as an ECG. For zone-specific training where accuracy matters — particularly Zone 2 and Zone 4 work — a chest strap is noticeably more reliable than optical.
FAQ
What is a heart rate zone calculator?
A heart rate zone calculator takes your age (and optionally your resting heart rate) and divides your training intensity into five zones — from very light recovery effort at Zone 1 to maximum-intensity sprints at Zone 5. Each zone is expressed as a beats-per-minute range based on a percentage of your maximum heart rate.
How do you calculate max heart rate?
The standard formula is 220 minus your age. A 40-year-old has an estimated max heart rate of 180 bpm. For people over 40, the Tanaka formula (208 − 0.7 × age) is more accurate. For women, the Gulati formula (206 − 0.88 × age) gives better results. None of these is exact — individual variation can be ±10–15 bpm.
How do you calculate heart rate from an ECG?
Count the number of large squares between two consecutive R waves (the tall spikes) and divide 300 by that number. If there are 4 large squares, the heart rate is 75 bpm. For irregular rhythms, count the QRS complexes in a 10-second strip and multiply by 6.
What heart rate is Zone 2?
Zone 2 is 60–70% of your maximum heart rate. For a 40-year-old with a max HR of 180 bpm, Zone 2 sits between 108 and 126 bpm. You should be able to hold a conversation in Zone 2 without gasping — if you can’t, you’ve moved into Zone 3.
What is the fat-burning heart rate zone?
The fat-burning zone is 60–70% of your max heart rate — the same range as Zone 2. At this intensity, fat provides the primary fuel source. To find it: multiply your max heart rate by 0.60 for the lower bound and 0.70 for the upper bound.
How accurate is the 220 minus age formula?
The 220-minus-age formula has a standard deviation of roughly ±12 bpm, meaning most people’s true max HR falls within 12 beats of the calculated figure. About 5% of people fall outside that range. The formula consistently underestimates max HR in older, fitter adults. A lab VO2 max test or a graded exercise test under medical supervision is the only way to find your true maximum.
How do I calculate training heart rate for a specific intensity?
Use the Karvonen formula: Target HR = ((Max HR − Resting HR) × target intensity %) + Resting HR. For a 45-year-old targeting 75% intensity with a max HR of 175 and resting HR of 60: ((175 − 60) × 0.75) + 60 = 86.25 + 60 = 146 bpm.
How do smartwatches calculate heart rate zones?
Most devices — Apple Watch, Garmin, Fitbit — default to the 220-minus-age formula unless you enter a custom max heart rate. Some Garmin devices use auto-detected max HR from workout peaks. You can manually set your max heart rate in device settings to improve zone accuracy.