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Calculator Answers

Heart Rate Calculator

Source: Karvonen MJ, Kentala E, Mustala O. The effects of training on heart rate: a longitudinal study. Ann Med Exp Biol Fenn. 1957;35(3):307-315 · Source verified July 22, 2026

Blake Boege
Written by Blake Boege · Founder, Calculator Answers

A heart rate calculator is a fitness assessment tool that estimates an individual's maximum heart rate and outlines target heart rate zones for physical exercise. It utilizes mathematical models like the simple age-based formula or the Karvonen method, which incorporates resting pulse for a more personalized baseline. By calculating heart rate percentages, the tool classifies workout intensities into recovery, aerobic fat-burning, cardiovascular, and maximum anaerobic thresholds, enabling individuals to optimize their exercise programs and track cardiovascular health.

Calculate your estimated maximum heart rate and target exercise zones for aerobic activity, fat burning, and peak cardio performance using standard and Karvonen formulas.

See also: Target Heart Rate Calculator and Blood Pressure Calculator.

Quick Answer

Calculate your target training heart rate zones for different exercise intensities. Enter your age and resting heart rate to view maximum and target heart rate ranges.

years

e.g. 35

Estimated max HR uses 220 − age. Karvonen adds resting heart rate to give a more individualized target.

Target heart rate

Estimated max HR

185 bpm

Percent-of-max method

Moderate (AHA)93 to 130 bpm
Vigorous (AHA)130 to 157 bpm
Zone 1 (very light)93 to 111 bpm
Zone 2 (light)111 to 130 bpm
Zone 3 (moderate)130 to 148 bpm
Zone 4 (hard)148 to 167 bpm
Zone 5 (max)167 to 185 bpm

Estimates only. People with cardiac conditions, on rate-affecting medication (such as beta-blockers), pregnant, or with symptoms during exercise should ask a clinician before training to target zones.

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Examples

Age 30, simple percent of max method

max ≈ 190 · moderate 95 to 133 · vigorous 133 to 162

Age 45, simple percent of max method

max ≈ 175 · moderate 88 to 123 · vigorous 123 to 149

Age 30, resting 60, Karvonen method

reserve 130 · moderate 125 to 151 · vigorous 151 to 171

How it works

Formula · Target HR = ((HRmax − resting HR) × intensity %) + resting HR. The heart-rate reserve idea is Karvonen 1957; the rearrangement into a target and the 220 − age maximum are later convention and are not in that paper

The 5 heart rate training zones

Your maximum heart rate (220 minus your age) gets divided into five training zones, each with a different fitness benefit:

ZONE 1 — VERY LIGHT (50-60% of max HR): Recovery and warm-up zone. Easy to maintain conversation. Used for warm-ups, cool-downs, and recovery between hard workouts.

ZONE 2 — LIGHT / FAT BURNING (60-70% of max HR): Often called the 'fat burning zone' because the body uses a higher percentage of fat for fuel here. Sustainable for hours. Best for building aerobic base and endurance.

ZONE 3 — MODERATE / CARDIO (70-80% of max HR): The 'cardio zone.' Improves cardiovascular fitness and aerobic capacity. You can talk in short sentences but can't hold a long conversation. Sustainable for 30-60 minutes.

ZONE 4 — HARD / THRESHOLD (80-90% of max HR): Lactate threshold zone. Builds speed and improves your body's ability to clear lactic acid. Sustainable for 10-20 minutes. Used in interval training.

ZONE 5 — MAXIMUM / PEAK (90-100% of max HR): All-out effort. Builds VO2 max and explosive power. Sustainable for only 1-5 minutes per interval. Used in high-intensity interval training (HIIT).

How the math works

Max HR is estimated as 220 minus age. Zones are percentages of that max. Karvonen adds resting HR to the math, which personalizes the target ranges based on your starting fitness.

Max HR · HRmax ≈ 220 − age (convention, not Karvonen's)

Percent of max · target = intensity × HRmax

Karvonen · target = resting + intensity × (HRmax − resting)

AHA moderate ~50 to 70% · vigorous ~70 to 85%.

Fat burning vs. cardio zones

The 'fat burning zone' (Zone 2, 60-70% of max HR) does use a higher PERCENTAGE of fat for fuel, but it burns FEWER total calories per minute than the cardio zone. The misleading name comes from this percentage-vs-total confusion.

Example: A 30-year-old (max HR 190) in Zone 2 (133 bpm) might burn 8 calories/minute with 50% from fat = 4 fat calories/minute. The same person in Zone 3 (152 bpm) might burn 12 calories/minute with 35% from fat = 4.2 fat calories/minute — slightly MORE fat burning despite the lower percentage.

For fat loss, total calorie burn matters more than the 'fat burning percentage.' Higher-intensity workouts in Zone 3-4 typically burn more total fat per workout, plus they keep your metabolism elevated for hours after.

Karvonen formula vs. simple formula

There are two primary ways to calculate target heart rate:

SIMPLE METHOD: Target HR = Max HR × intensity percentage
Example: A 30-year-old at 70% intensity = (220-30) × 0.70 = 133 bpm

KARVONEN FORMULA (more accurate): Target HR = ((Max HR - Resting HR) × intensity %) + Resting HR
Example: A 30-year-old with resting HR of 65 at 70% intensity = ((190-65) × 0.70) + 65 = 152 bpm

The Karvonen formula accounts for your individual resting heart rate, which varies based on fitness level. A highly fit person with a low resting HR gets a lower Karvonen target than someone with a higher resting HR at the same intensity percentage.

Related health tools

Configure and track your physical training goals with these related health calculators:

Target Heart Rate CalculatorBMI CalculatorTDEE Calculator

Health note. Estimated heart rate zones are for general guidance. Consult a medical professional before starting any new or vigorous exercise program, particularly if you have cardiovascular conditions or take heart rate-altering medications.

Related Calculators

More tools from Health

Target Heart Rate CalculatorEstimate maximum heart rate and target training zones from age. Supports percent-of-max and Karvonen heart-rate reserve methods.Blood Pressure CalculatorClassify a blood pressure reading using AHA-style adult categories: Normal, Elevated, Stage 1, Stage 2, and Hypertensive crisis.

Frequently asked questions

The most common way to estimate maximum heart rate is 220 minus your age (in beats per minute). For a 40-year-old, the estimated max HR is 180 bpm. While useful as a starting point, individual actual max HR can vary by 10 to 15 bpm.

Zone 1 (very light) is 50-60% of max HR, Zone 2 (light/aerobic) is 60-70%, Zone 3 (moderate) is 70-80%, Zone 4 (hard/threshold) is 80-90%, and Zone 5 (maximum effort) is 90-100% of max HR.

The calculation is target HR = resting HR + (intensity % × reserve), where the reserve is maximum minus resting heart rate, and it personalises the range to your own resting rate. The idea underneath, expressing intensity as a share of the range from rest to maximum rather than of the maximum alone, IS Karvonen's: his 1957 paper concluded that training heart rate "has to be more than 60 per cent of the available range from rest to the maximum attainable by running". Two things commonly attached to his name are NOT in that paper. It contains no rearrangement into a target heart rate, which later writers derived, and no age-based estimate of maximum heart rate at all; his six subjects had their maxima MEASURED by running them to exhaustion. Karvonen told an interviewer in 2000 that he had never published original research on the 220 minus age formula. So treat the reserve as his and the two things wrapped around it as convention.

Zone 2 (60-70% of max HR) is often called the fat-burning zone because your body burns a higher percentage of calories from fat rather than carbohydrates. However, higher-intensity zones burn more total calories overall, which is often more effective for total fat loss.

Briefly reaching your max heart rate during intense intervals is generally safe for healthy individuals. However, you should not sustain maximum effort for long periods. If you have any underlying cardiovascular conditions, consult your doctor for custom guidelines.