Skip to content
H HT99.
Read Articles
Everyday Utilities Free • No signup • Instant results

Heart Rate Zone Calculator

Find your target heart rate zones for cardio training.

years
bpm

About the Heart Rate Zone Calculator

This heart rate zone calculator computes your five training zones using the Karvonen formula, which accounts for your resting heart rate (a measure of individual cardiovascular fitness) rather than using a generic percentage of maximum heart rate alone. Enter your age and resting heart rate, and the tool returns your maximum heart rate, heart rate reserve, and the BPM ranges for each of the five training zones — from very light recovery to peak anaerobic effort.

Training in specific heart rate zones produces specific physiological adaptations. Zone 2 (60-70% of reserve) builds aerobic endurance and burns fat efficiently; Zone 3 (70-80%) improves cardiovascular fitness and lactate threshold; Zone 4 (80-90%) increases anaerobic capacity and VO2 max; Zone 5 (90-100%) develops peak power for short intervals. A well-designed training plan uses a mix of zones — typically 80% easy (Zones 1-2) and 20% hard (Zones 4-5) for endurance athletes.

The Karvonen formula is more accurate than the simple 'percentage of max HR' method because it accounts for individual fitness. A trained athlete with a resting HR of 45 will have lower zone targets than an untrained person with resting HR of 75, even at the same age — their cardiovascular system is more efficient.

How It Works

The Karvonen formula:

Target HR = ((Max HR - Resting HR) * intensity%) + Resting HR

Where:

  • Max HR = 220 - age (the classic formula; Tanaka et al. 2001 suggests 208 - 0.7*age as more accurate)
  • Resting HR = measured upon waking, before getting out of bed
  • Heart Rate Reserve (HRR) = Max HR - Resting HR
  • Intensity % = the fraction of reserve to use (0.5 for Zone 1, up to 1.0 for Zone 5)

The five training zones:

  • Zone 1 (50-60% HRR): Very light — recovery, warm-up, cool-down. Conversational pace, sustainable for hours.
  • Zone 2 (60-70% HRR): Light — aerobic endurance, fat oxidation. The 'all-day pace' for ultra-endurance.
  • Zone 3 (70-80% HRR): Moderate — aerobic fitness, lactate threshold development. Comfortably hard, sustainable 30-60 min.
  • Zone 4 (80-90% HRR): Hard — anaerobic threshold, VO2 max training. Heavy breathing, sustainable 10-30 min.
  • Zone 5 (90-100% HRR): Max — peak power, neuromuscular development. Sprint intervals, 30 sec - 5 min max.

Worked Examples

For a 30-year-old with resting HR 65 bpm:

  1. Max HR: 220 - 30 = 190 bpm
  2. Heart Rate Reserve (HRR): 190 - 65 = 125 bpm
  3. Zone 1 (50-60% HRR): 125 * 0.5 + 65 = 128 bpm to 125 * 0.6 + 65 = 140 bpm
  4. Zone 2 (60-70%): 140-153 bpm
  5. Zone 3 (70-80%): 153-165 bpm
  6. Zone 4 (80-90%): 165-178 bpm
  7. Zone 5 (90-100%): 178-190 bpm

Compare with a 30-year-old trained athlete, resting HR 45 bpm:

  1. HRR: 190 - 45 = 145
  2. Zone 2: 145 * 0.6 + 45 = 132 to 145 * 0.7 + 45 = 146 bpm

The trained athlete's Zone 2 upper bound (146 bpm) is actually lower than the untrained person's (153 bpm) at the same age — illustrating how fitness shifts zone targets. This is the key insight the Karvonen formula captures that simple % of max HR does not.

When to Use This Tool

Use this heart rate zone calculator when:

  • Setting training intensity targets for running, cycling, rowing, or other cardio
  • Designing a polarized training plan (80% easy, 20% hard)
  • Using a heart rate monitor (chest strap or wrist optical) to guide workout intensity
  • Building a base endurance phase (lots of Zone 2)
  • Adding high-intensity interval training (HIIT) in Zones 4-5
  • Recovery day pacing (stay in Zone 1)
  • Comparing heart rate zones before and after a fitness intervention

For race-pace estimation: a 10K race typically falls in Zone 4-5; a marathon in Zone 3-4; an ultra in Zone 2-3. Train the zones you'll race in.

Limitations & Disclaimer

This calculator uses the Karvonen formula with the classic Fox formula (220 - age) for max HR estimation, which has a standard error of ±10-12 bpm. The Tanaka formula (208 - 0.7 * age) is more accurate for adults over 40 but is not applied here. Zone targets are estimates — individual variation in actual max HR, lactate threshold, and VO2 max means your personal zones may differ by 5-15 bpm from the calculator's output. The calculator does not account for heart rate variability due to fatigue, dehydration, heat, caffeine, medications (beta-blockers, stimulants), stress, or altitude — all of which can shift your HR by 5-15 bpm at any given effort. The 50-60%, 60-70%, etc. zone boundaries are conventional, not based on sharp physiological transitions. For precise training prescription, get a lab VO2 max test with lactate threshold measurement. This is an educational tool, not medical advice. Individuals with cardiovascular conditions should consult a physician before starting vigorous exercise. See our disclaimer for full terms.

Frequently Asked Questions

How do I measure my resting heart rate?

Measure upon waking, before getting out of bed, after a good night's sleep. Use a heart rate monitor or count your pulse at the wrist (radial artery) or neck (carotid artery) for 60 seconds. Average over 3-5 mornings for accuracy. Resting HR is a useful fitness metric — it typically drops 1-2 bpm per month of endurance training as stroke volume increases.

Is the 220 - age formula accurate?

It's a rough estimate with standard error of ±10-12 bpm. The Tanaka formula (208 - 0.7 * age) is more accurate for adults over 40. The most accurate method is a maximal exercise test in a lab. For most training purposes, the 220 - age estimate is adequate — adjust based on perceived exertion and race performance.

What if my actual max HR differs from the estimate?

Very common. If you can sustain a heart rate above your estimated max (e.g., hitting 195 bpm when estimate says 190), your true max is higher — adjust your zones upward. Conversely, if you cannot reach the estimated max despite maximal effort, your true max is lower — adjust zones downward. Field test your max HR with a 5-minute all-out effort (after warming up) or a 30-15 IFT test.

What is the difference between % of max HR and % of HRR?

% of max HR (simple method) ignores resting HR. % of HRR (Karvonen method) accounts for resting HR, giving lower zone targets for fit individuals (low resting HR) and higher targets for less-fit individuals (high resting HR). HRR-based zones are more individualized and physiologically accurate, especially for trained athletes. Use Karvonen if you know your resting HR.

How long should I spend in each zone?

For endurance athletes, the 'polarized' (80/20) model is well-supported: 80% of training time in Zones 1-2 (easy), 20% in Zones 4-5 (hard), minimal Zone 3 (the 'gray zone' that's too hard for recovery but too easy for adaptation). For general fitness, 3-4 hours/week in Zones 2-3 plus 1-2 HIIT sessions in Zones 4-5 is effective.

Are heart rate zones the same as VO2 max zones?

Closely related but not identical. VO2 max zones are based on oxygen consumption, which correlates with but is not identical to heart rate. Zone 4-5 training increases VO2 max; Zone 2 builds the aerobic base that supports VO2 max. For precise VO2-based training, get a lab VO2 max test (with lactate threshold measurement); for general training, heart rate zones are adequate.

Last updated: July 21, 2026  ·  Author: HT99 Tools Editorial Team  ·  Reviewed by: HT99 Tools Editorial Team