Heart Rate Zone Calculator
Karvonen method — 5 training zones, VO₂max estimate, and max HR comparison.
Your Heart Rate Data
Measure first thing in the morning. Average adult: 60–80 bpm.
Enter your age and resting HR, then click Calculate
Methodology
Max HR: Fox formula: 220 − age (Fox & Haskell, 1971). Tanaka formula: 208 − (0.7 × age) (Tanaka et al., 2001) — generally more accurate for adults over 40.
Karvonen Method: THR = ((Max HR − Resting HR) × intensity%) + Resting HR. First published by Martti Karvonen, 1957. Accounts for fitness level via heart rate reserve (HRR).
VO₂max (Uth formula): VO₂max ≈ 15 × (Max HR / Resting HR). Uth N et al., 2004. Moderate accuracy (±10%) without laboratory testing.
References: American Heart Association (2021). Target Heart Rates Chart. Fox SM & Haskell WL (1971). Karvonen M et al. (1957). Ann Med Exp Biol Fenn 35(3). Tanaka H et al. (2001). J Am Coll Cardiol 37(1).
FAQ
What is the Karvonen method?
Karvonen formula calculates target HR using HR reserve (HRR = max HR − resting HR). THR = (HRR × intensity%) + resting HR. This accounts for your fitness level unlike simple % of max HR.
What are the 5 heart rate training zones?
Zone 1 (50–60%): Recovery. Zone 2 (60–70%): Aerobic base/fat burn. Zone 3 (70–80%): Aerobic endurance. Zone 4 (80–90%): Lactate threshold. Zone 5 (90–100%): VO₂max. Train 80% of volume in Zone 2.
How is VO₂max estimated from heart rate?
Uth formula: VO₂max ≈ 15 × (Max HR / Resting HR). For max HR 190, resting HR 60: VO₂max ≈ 47.5 ml/kg/min. Accurate measurement requires lab testing.
How do I find my maximum heart rate?
220 − age (Fox, 1971) is the most common. 208 − (0.7 × age) (Tanaka, 2001) is more accurate for adults. A graded exercise test gives the most precise value.
Calculate your five aerobic training zones with the Karvonen heart-rate-reserve method, compare two estimates of maximum heart rate, and get a target heart rate for any chosen intensity.
How it works
HRmax is the highest sustainable heart rate during exhaustive exercise. The classic Fox formula 220 − age has a standard error of ±10–12 bpm. Tanaka's 208 − 0.7 × age is statistically more accurate, especially for adults over 40.
Karvonen's method is preferred over %HRmax because it uses heart-rate reserve (HRmax − HRrest), which scales the zones to your individual fitness.
Five common zones are: Z1 50–60 %, Z2 60–70 %, Z3 70–80 %, Z4 80–90 %, Z5 90–100 % of HRR. Most aerobic adaptation happens in Z2; high-intensity intervals target Z4–Z5.
Formulas
- HRmax (Fox):
HRmax = 220 − age— Population estimate, ±10 bpm. - HRmax (Tanaka):
HRmax = 208 − 0.7 × age— More accurate for older adults. - HR reserve:
HRR = HRmax − HRrest— Working range above resting. - Karvonen target:
THR = HRR × intensity% + HRrest— Per-zone heart rate.
Worked examples
Zones for a 30-year-old
Inputs: Age 30, resting HR 60.
HRmax ≈ 190HRR = 190 − 60 = 130Z2 (60–70 %) = 138–151 bpmZ4 (80–90 %) = 164–177 bpm
Result: Z2 138–151, Z4 164–177 bpm.
Use cases
- Plan structured interval workouts
- Set Z2 base-training pace
- Pick a sustainable threshold zone
- Compare watch-based zones to literature-based zones
- Decide an intensity for warm-up and cool-down
Common mistakes to avoid
- Using %HRmax instead of Karvonen %HRR for low intensities
- Trusting 220 − age as exact
- Not measuring true resting HR (take it on waking)
- Drifting upward in heat or dehydration without adjusting
Limitations
- HRmax estimates have ±10 bpm error
- Beta-blockers and some medications lower HRmax substantially
- Trained athletes may need lab testing for exact zones
- Cardiac drift can elevate HR 5–10 bpm in long workouts
References
- Ainsworth BE et al. 2011 Compendium of Physical Activities. Med Sci Sports Exerc. 2011;43(8):1575–1581.
- American College of Sports Medicine. ACSM's Guidelines for Exercise Testing and Prescription, 11th ed., 2021.
- Karvonen MJ, Kentala E, Mustala O. The effects of training on heart rate. Ann Med Exp Biol Fenn. 1957;35(3):307–315.
- Tanaka H, Monahan KD, Seals DR. Age-predicted maximal heart rate revisited. J Am Coll Cardiol. 2001;37(1):153–156.
- Riegel PS. Athletic records and human endurance. American Scientist. 1981;69(3):285–290.
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Frequently asked questions
What is the Karvonen formula?
Target HR = (HRmax − HRrest) × intensity% + HRrest, using heart-rate reserve.
Fox vs Tanaka HRmax — which is better?
Tanaka has lower bias for adults over 40; Fox is fine for younger adults.
How do I measure resting HR?
Lying down, first thing in the morning before getting up — average over 3 days.
What zone is fat-burning?
Maximum fat percentage occurs around Z2 (60–70 % HRR), but absolute kcal from fat is similar across moderate intensities.
Are zones the same for cycling and running?
HR zones are similar, but cycling HRmax is often 5–8 bpm lower than running HRmax.
Why does my HR drift upward?
Cardiac drift from heat, dehydration, and fatigue can raise HR 5–10 bpm at the same effort.
What about beta-blockers?
They suppress HR — use perceived exertion instead and consult your clinician.
Can I rely on my watch?
Optical wrist sensors are usually within ±5 bpm in steady state; intervals can be unreliable.
Should I do all my training in Z5?
No — most plans use 80 % Z1–Z2 and 20 % Z4–Z5 (polarised model).
What is HRR vs HRmax %?
HRR uses your resting HR as a baseline; %HRmax does not. HRR adapts better to fitness changes.
Can pregnant individuals use this?
Many guidelines recommend perceived exertion over fixed HR zones during pregnancy.
Is this medical advice?
No — educational only.
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