Heart Rate Zone Calculator - Free Karvonen Target HR Solver

Compute your personal cardiovascular training zones using resting pulse rates and maximum heart rate formulas.

HR Zones Karvonen HRR Client-Side Only
years
bpm
Maximum Heart Rate (Tanaka)
187
HR Reserve: 127 bpm
Zone 1: Active Recovery (50% - 60%)
Warm-up, cooldown, and metabolic health.
124 — 136 bpm
Zone 2: Aerobic / Fat Burn (60% - 70%)
Endurance building and base cardiovascular health.
136 — 149 bpm
Zone 3: Tempo / Endurance (70% - 80%)
Aerobic power enhancement and training tempo.
149 — 162 bpm
Zone 4: Anaerobic Threshold (80% - 90%)
Lactate threshold increase and speed tolerance.
162 — 174 bpm
Zone 5: VO2 Max / Max Effort (90% - 100%)
Peak sprint training and maximum aerobic power.
174 — 187 bpm
Formula: (HR Reserve × intensity%) + Resting HR = Target HR

Understanding Heart Rate Zones

An endurance coach structuring a marathon runner's weekly training schedule sets specific heart rate zones to manage intensity. Training too hard too often can lead to overtraining syndrome, while training too light fails to stimulate cardiovascular adaptation. Heart rate monitoring provides an objective measure of cardiovascular stress.

Heart rate zones represent divisions of training intensities based on cardiac output, measured in beats per minute (bpm). By targeting specific heart rate ranges, you can isolate different metabolic systems (aerobic vs. anaerobic) and drive specific cardiorespiratory adaptations.

Physiology of Cardiovascular Intensity

During exercise, active muscles require oxygen to produce ATP (adenosine triphosphate) via oxidative pathways. To deliver this oxygen, the sympathetic nervous system triggers an increase in heart rate and stroke volume, elevating cardiac output. At lower intensities, the body relies primarily on fat oxidation for fuel. As intensity rises, it crosses the lactate threshold, transitioning to anaerobic carbohydrate metabolism and accumulating lactate in the blood.

Standard vs. Karvonen HRR Methods

Standard Method (% of Max HR): Simply divides maximum heart rate (e.g. 220 - age) into percentages. This method is blind to fitness level, treating a highly trained athlete with a resting pulse of 40 the same as a sedentary individual with a resting pulse of 80.

Karvonen Method (Heart Rate Reserve): Factors in your resting heart rate (RHR) to calculate your Heart Rate Reserve (HRR):

HRR = Max HR - Resting HR
Your target zones are then calculated from this reserve range:
Target HR = (HRR × Intensity %) + Resting HR
By anchoring the calculation at your actual resting pulse, the Karvonen method provides target zones that align more closely with physiological strain.

The Five Training Zones Explained

Technical Specifications

The calculator supports Tanaka (208 - 0.7 × age) and standard (220 - age) Max HR formulas. Karvonen zones are rounded to the nearest integer. If values overlap, the upper boundary of the lower zone marks the start of the next zone.

Frequently Asked Questions

How do I find my true resting heart rate?

Measure your pulse in the morning, immediately after waking up, while still in bed. Track it for three consecutive days and take the average to establish your baseline resting heart rate.

Does beta-blocker medication affect my zones?

Yes. Beta-blockers lower heart rate by blocking sympathetic nervous system activation. If you are taking cardiovascular medications, consult a cardiologist to establish target training heart rates using clinical stress testing.

Why does my heart rate increase during long workouts at the same pace?

This is known as cardiovascular drift. As you exercise, body temperature rises, prompting blood redirection to the skin for cooling. To maintain cardiac output as stroke volume slightly decreases from fluid loss (sweat), heart rate naturally rises.

VO2 Max Calculator — Estimates peak aerobic capacity.

Running Pace Calculator — Computes splits and race paces.

Calorie Burn Calculator — Calculates workout energy expenditures.