Target heart rate is the range of heartbeats per minute you should aim for during exercise to get the most benefit from your workout. It’s typically expressed as 50% to 85% of your maximum heart rate, which is estimated by subtracting your age from 220. A 40-year-old, for example, has an estimated maximum heart rate of 180 beats per minute, making their target range roughly 90 to 153 beats per minute depending on the workout intensity they’re going for.
How to Calculate Your Target Heart Rate
The most common formula is simple: subtract your age from 220 to get your estimated maximum heart rate, then multiply by the percentage range you want to hit. This is known as the Fox formula, and it’s the one you’ll see on gym posters and fitness apps. A 55-year-old would have an estimated max of 165, so exercising at moderate intensity (50% to 70%) means aiming for roughly 83 to 116 beats per minute.
There’s a more refined formula that tends to be more accurate for older adults: 208 minus 0.7 times your age. This is the Tanaka equation, and research on marathon runners has shown that the simpler 220-minus-age formula tends to underestimate maximum heart rate in older people. For a 65-year-old, the Fox formula gives a max of 155, while the Tanaka equation gives 162. That seven-beat difference shifts the entire target range upward.
A third approach, called the Karvonen method, factors in your resting heart rate for a more personalized number. You subtract your resting heart rate from your maximum heart rate to get your “heart rate reserve,” then multiply by your desired intensity percentage, and add your resting heart rate back. If your max is 180, your resting rate is 60, and you want to train at 70% intensity, the math looks like this: (180 – 60) × 0.70 + 60 = 144 beats per minute. Because it accounts for your baseline fitness level, this method gives a more tailored target.
What the Heart Rate Zones Mean
Fitness professionals break heart rate intensity into five zones, each producing different effects in your body:
- Zone 1 (50% to 60% of max): Very light effort. This is a warm-up pace or easy recovery walk. You can hold a full conversation without any trouble.
- Zone 2 (60% to 70% of max): Light aerobic effort, sometimes called your “base” or endurance zone. You can talk comfortably but singing would be difficult. This is the sweet spot for building aerobic fitness over longer sessions.
- Zone 3 (70% to 80% of max): Moderate effort. You can speak in short phrases but not carry on a flowing conversation. Calories are split roughly evenly between fat and glycogen (your body’s stored carbohydrate energy).
- Zone 4 (80% to 90% of max): Hard effort. You can manage only a few words at a time. This zone builds speed and lactate tolerance.
- Zone 5 (90% to 100% of max): Maximum effort, sometimes called anaerobic or peak intensity. Sustainable for only short bursts, typically 30 seconds to a couple of minutes.
The CDC recommends adults get 150 minutes per week of moderate-intensity activity or 75 minutes of vigorous-intensity activity. One minute of vigorous exercise counts roughly the same as two minutes of moderate exercise. If you’re training in zones 2 and 3, you’re in moderate territory. Zones 4 and 5 count as vigorous.
The “Fat-Burning Zone” Is Misleading
You may have seen treadmills label zone 1 or 2 as the “fat-burning zone.” There’s a kernel of truth here: at lower intensities, your body does pull a higher percentage of its fuel from fat rather than glycogen. But the total number of calories burned is much lower than at higher intensities, which matters more for weight loss.
During high-intensity exercise, your body burns through glycogen stores quickly, then shifts to tapping fat stores. The result is that a harder workout burns more total calories, including more total fat calories, even though fat makes up a smaller percentage of the fuel mix. If your goal is losing weight, the intensity that helps you burn the most total calories wins. For most people, that means working in zones 3 through 5 rather than staying in the low-effort range.
How Accurate Are Wrist Monitors?
Chest strap monitors remain the gold standard for accuracy outside a clinical setting. In a study comparing commercial devices against a medical-grade ECG, the Polar H7 chest strap had the highest agreement at 98%, followed closely by the Apple Watch at 96%. Wrist-worn optical sensors from Fitbit, Garmin, and TomTom came in around 89% agreement at lower exercise intensities.
The real problem with wrist sensors shows up during intense exercise. At running speeds of 8 and 9 miles per hour, none of the wrist-worn devices in that study met the threshold for acceptable accuracy. Movement at high speeds causes the sensor to bounce against the skin, disrupting the optical signal. If you’re doing interval training or sprints and want reliable numbers, a chest strap is worth the investment. For steady-state jogging or cycling, a wrist device gives you a reasonable estimate.
When Standard Formulas Don’t Apply
Beta-blockers, commonly prescribed for high blood pressure and certain heart conditions, slow your heart rate by design. That means the standard age-based formulas will overshoot your actual target. If you take beta-blockers and try to hit a heart rate calculated from 220 minus your age, you may push yourself dangerously hard trying to reach a number your medication won’t let your heart achieve. The American Heart Association recommends that people on beta-blockers work with their healthcare provider to determine a personalized target, often through a brief exercise stress test, because the drugs affect everyone differently.
An alternative is the “talk test,” which doesn’t rely on heart rate numbers at all. At moderate intensity, you should be able to talk but not sing. At vigorous intensity, you can manage only a few words before needing a breath. This simple gauge works for anyone whose heart rate response is altered by medication, and it’s surprisingly reliable even for people who aren’t on any drugs.
Putting It Into Practice
If you’re new to heart rate training, start by finding your estimated maximum (220 minus your age for a quick number, or 208 minus 0.7 times your age for a slightly more accurate one). Multiply by 0.50 and 0.70 to get your moderate-intensity range. That’s the zone most general fitness guidelines point to for health benefits.
Check your heart rate about 10 minutes into exercise, either with a monitor or manually. To check manually, press two fingers against the inside of your wrist or the side of your neck, count beats for 15 seconds, and multiply by four. If you’re below your target range, pick up the pace. If you’re above it and not intentionally doing high-intensity work, ease off. Over weeks of consistent training, you’ll notice that activities that once pushed you into zone 4 start to feel more like zone 3. That shift is your cardiovascular fitness improving, and it’s one of the most practical reasons to track your heart rate in the first place.