To calculate your target heart rate, estimate your maximum heart rate (commonly 220 minus your age), then multiply it by the intensity you want. The American Heart Association (AHA) defines moderate exercise as 50% to 70% of maximum and vigorous as 70% to 85%. For a 45-year-old, maximum heart rate is about 175 beats per minute (bpm), so the moderate zone is about 88 to 123 bpm and the vigorous zone 123 to 149 bpm. If you know your resting heart rate, the Karvonen formula gives a more personal range.
Step 1: Estimate maximum heart rate
| Formula | Equation | Age 45 |
|---|---|---|
| Traditional (Fox) | 220 − age | 175 bpm |
| Tanaka (2001) | 208 − 0.7 × age | 177 bpm |
| Gulati (women, 2010) | 206 − 0.88 × age | 166 bpm |
All three are population averages, and real maximums vary widely, often by 10 to 20 bpm or more from the estimate. The Tanaka equation tends to fit adults over 40 better; the Gulati equation came from a large study of women’s exercise tests. A supervised graded exercise test is the only way to measure your actual maximum.
Step 2: Choose a target intensity
Two widely cited sets of ranges:
| Source | Moderate intensity | Vigorous intensity |
|---|---|---|
| American Heart Association | 50%–70% of HRmax | 70%–85% of HRmax |
| CDC | 64%–76% of HRmax | 77%–93% of HRmax |
For the 45-year-old with an estimated maximum of 175 bpm:
- AHA moderate: 175 × 0.50 to 175 × 0.70 = 88 to 123 bpm
- AHA vigorous: 175 × 0.70 to 175 × 0.85 = 123 to 149 bpm
- CDC moderate: 175 × 0.64 to 175 × 0.76 = 112 to 133 bpm
- CDC vigorous: 175 × 0.77 to 175 × 0.93 = 135 to 163 bpm
The ranges differ because the organizations draw the line between moderate and vigorous differently; both are reasonable guides. The target heart rate calculator shows both methods and five training zones.
Target heart rate by age
Using 220 − age and the AHA percentages:
| Age | Max HR (220 − age) | Max HR (Tanaka) | 50% | 70% | 85% |
|---|---|---|---|---|---|
| 20 | 200 | 194 | 100 | 140 | 170 |
| 25 | 195 | 191 | 98 | 137 | 166 |
| 30 | 190 | 187 | 95 | 133 | 162 |
| 35 | 185 | 184 | 93 | 130 | 157 |
| 40 | 180 | 180 | 90 | 126 | 153 |
| 45 | 175 | 177 | 88 | 123 | 149 |
| 50 | 170 | 173 | 85 | 119 | 145 |
| 55 | 165 | 170 | 83 | 116 | 140 |
| 60 | 160 | 166 | 80 | 112 | 136 |
| 65 | 155 | 163 | 78 | 109 | 132 |
| 70 | 150 | 159 | 75 | 105 | 128 |
Notice that the two maximum-heart-rate formulas agree around age 40 and diverge with age: by 70, Tanaka’s estimate is 9 bpm higher.
The Karvonen method (heart rate reserve)
The percentage-of-maximum method ignores fitness. Two people of the same age, one with a resting heart rate of 50 and one of 80, get the same zones. The Karvonen formula uses your heart rate reserve (HRR), the gap between maximum and resting heart rate:
Example: age 45, resting heart rate 65 bpm.
- HRR = 175 − 65 = 110
- 50%: 110 × 0.50 + 65 = 120 bpm
- 70%: 110 × 0.70 + 65 = 142 bpm
- 85%: 110 × 0.85 + 65 = 158.5 bpm
Karvonen targets are higher than simple percentages at the same intensity, because they start from resting heart rate rather than zero. The two methods use different scales, so do not mix them: 70% of HRR is a harder effort than 70% of maximum.
To measure resting heart rate, count your pulse for a full minute after waking, before getting out of bed, on three mornings, and average the results.
Five training zones
Many coaches and fitness devices divide effort into five zones, usually as percentages of maximum heart rate:
| Zone | % of max HR | Feels like | Age 45 (max 175) |
|---|---|---|---|
| 1 – Very light | 50%–60% | Easy, recovery | 88–105 |
| 2 – Light | 60%–70% | Comfortable, conversational | 105–123 |
| 3 – Moderate | 70%–80% | Breathing harder, short sentences | 123–140 |
| 4 – Hard | 80%–90% | Few words at a time | 140–158 |
| 5 – Maximum | 90%–100% | All-out, only for short intervals | 158–175 |
How much exercise to aim for
The Physical Activity Guidelines for Americans, published by the Department of Health and Human Services, recommend that adults get at least 150 minutes of moderate-intensity or 75 minutes of vigorous-intensity aerobic activity a week, or an equivalent mix, plus muscle-strengthening activity on two or more days. Heart rate targets are one way to confirm you are actually in the moderate or vigorous range. Running and walking pace can be planned with the pace calculator, and energy use estimated with the calories burned calculator.
Checking your heart rate
- Manual pulse: place two fingers on the inside of your wrist or the side of your neck. Count beats for 15 seconds and multiply by 4.
- Chest strap: the most accurate consumer option during exercise.
- Wrist or watch sensors: convenient, but may lag or misread during intervals, cold weather or strength training.
When heart rate is not the right guide
- Medications such as beta-blockers blunt the heart rate response.
- Heat, dehydration, caffeine and stress raise heart rate at the same effort.
- Pregnancy changes cardiovascular response; current guidance favors the talk test and perceived exertion.
- Heart conditions require individualized targets from your doctor.
In these cases, use the talk test (you can talk but not sing at moderate intensity; you can say only a few words at vigorous intensity) or a rating of perceived exertion. As fitness improves, your resting heart rate often drops; the VO2 max calculator tracks aerobic fitness more directly.
For how exercise fits into an energy budget, see how to calculate calories for weight loss.
This guide is for general education, not medical advice. Check with a healthcare professional before starting a vigorous exercise program, especially if you have heart disease, high blood pressure, diabetes or take medications that affect heart rate. Stop exercising and seek care if you have chest pain, faintness or unusual shortness of breath.
Frequently asked questions
What is my target heart rate at 45?
Using the common 220 − age estimate, maximum heart rate is 175 beats per minute. The American Heart Association's moderate range of 50% to 70% is about 88 to 123 bpm, and its vigorous range of 70% to 85% is about 123 to 149 bpm.
Is 220 minus age accurate?
It is a rough average. Individual maximum heart rates can differ from it by 10 to 20 beats per minute or more. The Tanaka formula, 208 − 0.7 × age, fits research data better for older adults, but only a supervised exercise test measures your true maximum.
What is the Karvonen formula?
It sets targets using heart rate reserve, the difference between maximum and resting heart rate: target = (max − resting) × intensity + resting. It personalizes zones for people with very low or high resting heart rates.
How do I check my heart rate during exercise?
Find your pulse at the wrist or the side of the neck, count beats for 15 seconds and multiply by 4. Chest-strap monitors are more accurate than wrist-based optical sensors, especially during intervals.
Do medications affect target heart rate?
Yes. Beta-blockers and some other heart and blood pressure medications lower heart rate, so standard target zones may not apply. People taking them should ask their doctor for a target and use perceived exertion instead.