Target Heart Rate: 220−Age vs Karvonen (and Tanaka)

DevOkk's Target Heart Rate Calculator compares the textbook estimates side by side: Fox (220−age), optional Tanaka (208−0.7×age), and Karvonen zones when you enter resting HR. Defaults are age 30, rest 60 bpm. At 70% intensity, Fox alone gives 133 bpm; Karvonen with rest 60 gives 151 bpm. That 18-beat gap is not a bug. It is two different definitions of "70%."

This is fitness education, not medical advice. Not a stress test. Not clearance after chest pain. Not dosing for blood pressure medication. If you need clinical exercise prescription, use a clinician.

Pace on the road is Pace vs speed. Session energy is METs and calories burned. Daily calories are BMR vs TDEE. More tools: Fitness Calculators.

Fox: the 220−age shorthand

The Fox equation estimates maximum heart rate as:

HRmax ≈ 220 − age

At age 30: 220 − 30 = 190 bpm.

Training zones are often published as percentages of that max:

Zone label	% of HRmax	Fox bpm (age 30)
Very light	50–60%	95–114
Light	60–70%	114–133
Moderate	70–80%	133–152
Hard	80–90%	152–171
Maximum	90–100%	171–190

70% of Fox max = 0.7 × 190 = 133 bpm. That is the number people remember from gym charts.

Where Fox came from matters less than what it is not. It is not your measured peak from a graded exercise test. Meta-analyses show standard deviation near 10–12 bpm around any age line. Two healthy 30-year-olds can have lab maxes of 175 and 205. Fox prints 190 for both.

Fox also ignores resting heart rate. A fit person with rest 48 and an untrained person with rest 78 get the same "70% max" target despite different reserves. That is why Karvonen exists.

Tanaka: a newer regression line

Tanaka et al. proposed:

HRmax ≈ 208 − 0.7 × age

At age 30: 208 − 21 = 187 bpm - 3 bpm lower than Fox.

70% of Tanaka max = 0.7 × 187 = 130.9 bpm (≈ 131).

Tanaka often tracks measured max slightly better in some cohorts, especially older adults. It is still a population line. DevOkk can display Tanaka alongside Fox so you see how much the choice of regression moves zone edges. Switching equations until you like the easier number is shopping, not training.

Karvonen: reserve, not raw max

The Karvonen method (heart rate reserve) is:

Target HR = (HRmax − HRrest) × intensity + HRrest

With Fox max 190, rest 60, 70%:

• Reserve = 190 − 60 = 130 bpm
• 70% of reserve = 130 × 0.7 = 91 bpm
• Add rest back: 91 + 60 = 151 bpm

Compare to Fox 70% = 133 bpm. Karvonen is 18 bpm higher at the same nominal percentage because "70%" applies to the swing between rest and max, not to max alone.

Intuition: at rest you are already at 60. The trainable range is 130 bpm wide. Karvonen says use 70% of that range above rest. Fox says use 70% of the ceiling from zero - which physiologically you never occupy.

DevOkk's default rest 60 exists to make that contrast visible. Measure rest before coffee, before news, lying or seated calmly for a minute - not mid-scroll. Watches that report "resting HR" overnight are smoother than a one-off panic reading.

If resting HR is at or above Fox max, the calculator rejects the input - the math breaks. That can happen with bad data entry, not because you are fine to ignore it.

Side-by-side at default 30 / 60

Using Fox max 190, rest 60:

Zone	Fox range	Karvonen (Fox) range
50–60%	95–114	125–138
60–70%	114–133	138–151
70–80%	133–152	151–164
80–90%	152–171	164–177
90–100%	171–190	177–190

The 60–70% "fat burn" band in Fox land is 114–133. In Karvonen it is 138–151. Same labels, different beats. No wonder people argue about "easy runs" on heart rate.

Tanaka Karvonen columns shift slightly lower because max is 187 instead of 190. The structural lesson is unchanged: method choice moves targets more than most gadgets admit.

This is not a stress test

A clinical exercise stress test monitors ECG, symptoms, and sometimes imaging while load increases under supervision. It can stop early for ischemia, arrhythmia, or hypotension. It produces individual data tied to diagnosis and clearance.

An online 220−age box produces 190 for every average 30-year-old on the internet. Those jobs do not overlap.

Do not use DevOkk's zones to:

• Self-clear chest pain or unexplained syncope
• Titrate medications that affect chronotropic response
• Replace cardiology follow-up after a stent or valve surgery
• Diagnose "overtraining" from one high reading

If a clinician gave you a specific cap ("do not exceed 120 bpm"), that instruction wins over any website.

Medications that rewrite the chart

Beta blockers (metoprolol, bisoprolol, propranolol, etc.) lower heart rate at a given workload. You might reach breathless at 125 bpm while the Fox chart says zone 2 starts at 114. Following the chart can under-train or over-reach depending on drug dose and beta-1 selectivity.

Calcium channel blockers, ivabradine, stimulants, decongestants, and thyroid hormone also move HR–effort coupling. Pacemakers cap or pace independently of your effort feeling.

The calculator cannot know your pharmacy list. Default zones assume no pharmacologic blunting. That assumption fails for a large fraction of adults over 50.

HRV, lactate threshold, and what zones miss

Heart rate variability (HRV) morning scores describe autonomic readiness, not "zone 3." Low HRV might suggest backing off; it does not replace a max estimate.

Lactate threshold (or ventilatory threshold) is where blood lactate accumulation accelerates - typically roughly 80–90% of HRmax in trained people, but individual spread is wide. Field tests (30-minute time trial, talk test) approximate threshold better than 220−age for steady-state pacing.

Rate of perceived exertion (RPE) still works when HR lies - heat, caffeine, sleep debt, menstrual cycle phase, and dehydration decouple pulse from power.

Smart pairing:

• Fox/Karvonen for a first-pass band on easy days
• RPE + pace from Pace Calculator for runs
• MET session estimates from Calories Burned Calculator for energy - still averages

None of those replace medical evaluation when symptoms appear.

Worked example: two runners, same age

Both age 30, Fox max 190.

Runner A: rest 48, fit. Karvonen 70% = (190−48)×0.7+48 = 147.4 bpm.

Runner B: rest 72, detrained. Karvonen 70% = (190−72)×0.7+72 = 154.6 bpm.

Fox 70% gives 133 bpm for both. Reality: A's easy run might feel easy at 145; B might need 155 to hit the same internal load - or B might fatigue faster despite higher HR because stroke volume differs.

The calculator exposes the math. It does not know VO₂max, hemoglobin, or heat acclimation.

Tanaka + Karvonen together

With Tanaka max 187, rest 60, 70% Karvonen:

(187−60)×0.7+60 = 148.9 bpm - about 2 bpm lower than Fox-based 151.

DevOkk's page can show both max models when toggled. Use the toggle to see sensitivity, not to pick the easier workout.

Privacy and limits

Age and resting HR run in JavaScript in your browser. No account. Drafts may sit in localStorage up to 30 days on that device. Clear on shared machines.

The page does not ingest Apple Health, Garmin, or Polar exports. It does not compute HR drift on long runs. It does not adjust for pool temperature in swim HR (which is noisy anyway).

BMI and weight screening are unrelated instruments: Why BMI is not a diagnosis.

Choosing a method without fooling yourself

Practical guidance for healthy adults using estimates for fitness:

1. Pick one framework (Fox-only or Karvonen with a honest rest) and hold it for a block of weeks.
2. Anchor easy days with RPE ("can speak in sentences") even if HR wanders.
3. Do not chase a zone when pace says you are sprinting downhill with tailwind.
4. Re-measure rest monthly; fitness drops resting HR slowly.
5. Escalate to medicine for chest pain, fainting, or palpitations - not a higher zone.

DevOkk shows 133 vs 151 at 70% on purpose. If your watch defaults to Fox and your coach speaks Karvonen, you are not "wrong" - you are misaligned on definitions. Align words before aligning beats.

Where to go next

Open Target Heart Rate Calculator with your age and a calm resting pulse. Compare Fox and Karvonen columns. Toggle Tanaka if you want to see regression choice.

Plan paces on Pace Calculator. Estimate session burn on Calories Burned Calculator. Browse Fitness Calculators for protein and strength tools.

The chest strap and the clinic stress lab still beat 220−age on questions that matter for disease. For everyday training bands, know which formula you are using - and that 70% is not universal across methods.