Online Calculators FreeReference Manual

Health Metrics Calculator

Twelve-plus body metrics from standard published equations in one dropdown: body fat by the BMI method, frame size, Harris-Benedict and Katch-McArdle BMR, Tanaka max heart rate with zones, Karvonen target rates, Cooper 12-minute-run VO₂max, sleep-cycle bedtimes, caffeine against the 400 mg limit, steps to distance, walking calories, protein per meal, blood-pressure categories, and body surface area. Every number is an estimate with its formula shown — screening arithmetic, not medical advice.

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CalculatorFORM HEALTH EXTRA CALCULATOR
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One page of screening arithmetic

Pick the measurement from the dropdown and the form adapts: four fields for the metabolism equations, two for a blood-pressure reading, one for max heart rate. Every result shows the substituted formula beneath the board, and every member carries a margin note about where its formula stops being trustworthy — because in health math, the error bars are the story.

The equations at a glance

Body fat (Deurenberg) 1.20×BMI + 0.23×age − 10.8×sex − 5.4. BMR — revised Harris-Benedict (Roza–Shizgal 1984) with Mifflin-St Jeor beside it, or Katch-McArdle 370 + 21.6×lean-kg when you know your body fat. Heart rate — Tanaka max 208 − 0.7×age; Karvonen target (max − rest)×intensity + rest. VO₂max (Cooper): (12-min meters − 504.9) ÷ 44.73. Sleep: 90-minute cycles counted back from your alarm. Caffeine: 400 mg/day FDA reference, 200 mg in pregnancy. BSA (Mosteller) √(cm × kg ÷ 3600). Blood pressure: the 2017 ACC/AHA bands.

Worked example

  1. A 30-year-old man, 70 kg, 175 cm: BMI 22.9 → Deurenberg body fat ≈ 18.1%.
  2. Same person: Harris-Benedict BMR ≈ 1,696 kcal/day (Mifflin-St Jeor says 1,649).
  3. Tanaka max heart rate at 30: 208 − 0.7×30 = 187 bpm; Karvonen 60% zone with rest 60/max 190 lands at 138 bpm.
  4. A 2,400 m Cooper run: (2400 − 504.9) ÷ 44.73 ≈ 42.4 ml/kg/min — dead average for men in their 30s.
  5. Mosteller BSA at 175 cm / 70 kg: √(175×70÷3600) ≈ 1.84 m².

How to use it

  1. Pick the measurement from the “Which measurement?” dropdown.
  2. Fill the fields that appear — switches for sex, units, and pace change the formula inputs.
  3. Read the board, the substituted formula, and the margin note about the estimate’s limits.
  4. Screenshot or share the link for your appointment — then let a clinician interpret it.

Frequently asked questions

How accurate is the BMI-based body fat estimate?

The Deurenberg equation has a standard error of roughly 4–5 percentage points. It was validated on adults 18–62 and skews high in muscular people and low in adults over 60. For a sharper home estimate use the tape-measure Navy method (in the diet calculator family); DEXA is the clinical reference.

Which BMR formula should I use?

If you know your body-fat percentage, Katch-McArdle (370 + 21.6 × lean kg) is usually sharpest. Otherwise modern reviews favor Mifflin-St Jeor slightly over the revised Harris-Benedict — this page shows both side by side so you can see the spread, which is typically 2–5%.

Why 208 − 0.7 × age instead of 220 − age?

Tanaka’s 2001 meta-regression of 351 lab-measured maxima fits better across ages, especially past 40 where 220 − age drifts high. Even so, both carry a standard deviation of 7–10 bpm — a formula zones you in, a graded test zones you exactly.

How does the Karvonen method differ from percentage-of-max zones?

Karvonen works from heart-rate reserve (max − resting), so a runner with a 50 bpm resting rate gets lower absolute targets at the same percentage than a stressed beginner with 70. Same intensity label, personalized floor.

Is 400 mg of caffeine a hard safety limit?

No — 400 mg/day is the FDA’s figure for healthy adults at which adverse effects stay uncommon, not a cliff edge. Pregnancy guidance is under 200 mg/day (ACOG), and slow caffeine metabolizers feel effects at far lower doses.

Can a calculator diagnose high blood pressure?

No. This member just sorts your numbers into the 2017 ACC/AHA bands (normal, elevated, stage 1, stage 2, crisis). Diagnosis needs multiple raised readings on separate occasions, properly taken — and anything above 180/120 is a call for immediate medical attention, not a second reading.