How the target heart rate calculator works
This calculator estimates your maximum heart rate from your age, then divides the range between resting and maximum into five training zones. Each zone targets a different physiological adaptation, from easy recovery to peak cardiovascular effort.
If you provide your resting heart rate, the calculator uses the Karvonen formula (based on heart rate reserve) for more personalized zones. Without it, simple percentages of max HR are used.
How to use it
- Enter your age.
- Enter your resting heart rate (optional but recommended for accuracy).
- Read your max HR, heart rate reserve, target aerobic range, and the five-zone breakdown in the table.
- Use the zone bar to see where your training intensities fall visually.
How to measure resting heart rate
For the most accurate zones, measure your resting heart rate correctly:
- Take it first thing in the morning, before getting out of bed.
- Measure for three consecutive mornings and average the readings.
- Count your pulse for a full 60 seconds (or 15 seconds × 4).
- Avoid measuring after a night of poor sleep, alcohol, or illness.
A well-trained endurance athlete might have a resting HR of 40–55 bpm. An average healthy adult is typically 60–80 bpm. A higher resting HR generally indicates lower cardiovascular fitness.
How target heart rate is calculated
Maximum heart rate
The default formula (Haskell & Fox, 1970) estimates max HR as:
This is a population average with a standard deviation of about 10–12 bpm. Your true max may be higher or lower. The Advanced section offers two alternative formulas (Tanaka, Nes) that may be more accurate for specific age groups.
The Karvonen formula (with resting HR)
When you provide a resting heart rate, the calculator uses heart rate reserve for more personalized zones:
This is more accurate because it accounts for your fitness level. A fit person with a low resting HR has a larger reserve and needs a higher absolute heart rate to reach the same relative intensity.
Simple percentage method (without resting HR)
Without resting HR, zones are calculated as simple percentages of max HR:
This is less personalized but still useful for general guidance.
Understanding the five training zones
Each zone produces different physiological adaptations:
Very light (50–60% HRR)
Warm-up, cool-down, and active recovery. Blood flow increases but there is minimal cardiovascular stress. Use this for the first 5–10 minutes of any session and for recovery days between hard efforts.
Light (60–70% HRR)
Base endurance and fat oxidation. You can hold a full conversation comfortably. This is the foundation of aerobic fitness and where most easy runs and long slow distance should fall. Building volume here improves mitochondrial density and capillary networks.
Moderate (70–80% HRR)
Aerobic conditioning and speed development. Conversation becomes choppy (you can speak in short sentences). This zone improves cardiac output and lactate clearance. Most tempo runs, steady-state cardio, and group fitness classes fall here.
Hard (80–90% HRR)
Threshold training and anaerobic development. Speaking is limited to a few words. Lactate accumulates faster than it clears. Intervals in this zone improve your lactate threshold, the intensity you can sustain for extended periods. Typical for hard interval work (3–8 minute efforts).
VO2 Max / Maximum (90–100% HRR)
Peak effort. No conversation possible. This zone develops maximum oxygen uptake (VO2max) and neuromuscular power. Only sustainable for 30 seconds to 3 minutes. Used in short intervals (200m–800m repeats, Tabata-style work). Requires adequate recovery between efforts.
How much time in each zone?
A common guideline for endurance athletes is the 80/20 rule: roughly 80% of training time in Zones 1–2 (easy), and 20% in Zones 3–5 (moderate to hard). Recreational exercisers benefit from a similar distribution. The most common mistake is spending too much time in Zone 3 (moderately hard but not hard enough to drive adaptation) and not enough in Zone 1–2 (genuinely easy).
Common mistakes to avoid
- Training in Zone 3 all the time. It feels productive but is too hard for recovery and too easy for peak adaptation. Go easier on easy days, harder on hard days.
- Using someone else's zones. Heart rate zones are individual. Two people the same age can have very different max and resting heart rates.
- Ignoring external factors. Heat, altitude, dehydration, caffeine, stress, and sleep all shift heart rate. If your heart rate is 10+ bpm higher than usual at the same effort, adjust expectations.
- Relying solely on the 220-minus-age formula. It has a ±12 bpm error margin. If your zones feel wrong (you can't speak in Zone 2, or Zone 4 feels easy), your true max may differ from the estimate. Consider a graded exercise test.
Limitations
Estimated max heart rate varies by ±10–12 bpm from the formula. The only way to know your true max is a maximal graded exercise test under medical supervision. Beta-blockers and other medications that affect heart rate make these formulas unreliable — consult your physician for adjusted targets. These zones do not apply to swimming (water immersion lowers HR by 10–15 bpm).
Frequently asked questions
What is the Karvonen formula?
The Karvonen formula calculates target heart rate using your heart rate reserve (max HR minus resting HR): THR = (HRR × intensity%) + resting HR. It is more personalized than a simple percentage of max HR because it accounts for your fitness level via your resting heart rate.
Which max heart rate formula should I use?
The Haskell & Fox formula (220 − age) is the most widely used and is fine for general fitness. Tanaka (208 − 0.7 × age) is considered slightly more accurate for older adults based on a 2001 meta-analysis. The Nes formula (211 − 0.64 × age) was derived from a large Norwegian study. All have a standard deviation of 10–12 bpm.
How do I measure my resting heart rate accurately?
Measure your pulse first thing in the morning before getting out of bed, ideally for three consecutive days and average the readings. Use your fingertips on your wrist (radial pulse) or neck (carotid). Count beats for 60 seconds, or for 15 seconds and multiply by 4. Avoid measuring after caffeine or a poor night of sleep.
What if I do not know my resting heart rate?
If you leave the resting heart rate field empty, the calculator uses simple percentages of your estimated maximum heart rate instead of the Karvonen method. The zones will be slightly less personalized but still useful for general training guidance. Average resting HR for adults is 60–80 bpm.
Which zone should I train in for weight loss?
While Zone 2 (fat burn, 60–70%) uses a higher proportion of fat for fuel, Zone 3 (cardio, 70–80%) burns more total calories per minute. For weight loss, total calorie expenditure matters most. A mix of Zone 2 and Zone 3, combined with a caloric deficit, is more effective than staying exclusively in the fat-burn zone.
Can medications affect my target heart rate zones?
Yes. Beta-blockers lower both resting and max heart rate significantly, making standard formulas inaccurate. Some stimulant medications raise resting HR. If you take heart-rate-affecting medication, consult your doctor for personalized zones or use perceived exertion (RPE scale) instead of heart rate targets alone.
Is it dangerous to exercise in Zone 5?
For healthy individuals, brief periods in Zone 5 (90–100%) during interval training are safe and effective for improving VO2max. However, sustained Zone 5 exercise is not recommended for beginners, people with cardiovascular conditions, or those without medical clearance. Build a Zone 2/3 base before adding high-intensity intervals.