Wellness Calculators: BMI, BMR, and Body Composition (DevOkk Hub)

Every page in the wellness hub runs in your browser. Measurements are not uploaded to complete the formulas. Drafts may sit in localStorage for up to 30 days on your device. No account. Not medical advice. Screening is not diagnosis. Calculators are not clearance to drive, diet, or lift through injury.

This roundup routes which wellness tool to open, what each can honestly claim, and where the blog cluster goes deeper.

Wellness vs fitness: two hubs, two jobs

Hub	Typical questions	Example tools
Wellness	"What WHO band am I in?" "Resting calories?" "Tape body fat?" "Due date from LMP?"	BMI, BMR, Body Fat, Due Date
Fitness	"What split for 10K?" "Estimated 1RM?" "METs for this jog?"	Pace, One-Rep Max, Calories Burned

Cross-over happens at calories: wellness owns BMR/TDEE foundations; fitness owns session METs. Read BMR vs TDEE vs calories burned before adding a run on top of a "very active" maintenance number.

Athletes with high muscle may sit in overweight BMI bands while tape body fat looks fine. That is BMI's blind spot, not proof the athlete is "unhealthy." Why BMI is not a diagnosis is the mandatory read before panic.

BMI and healthy weight: screening labels only

BMI Calculator computes kg ÷ m² (or imperial equivalent) and prints WHO adult bands for non-pregnant adults. Default 175 cm, 70 kg → ~22.86, labeled normal. The number does not see muscle, visceral fat, ethnicity-specific clinical cutoffs your doctor may use, or pediatric percentiles.

Sibling pages reframe the same physics:

• Healthy Weight Calculator - kg band for BMI 18.5–24.9 at a height
• Overweight Calculator - cutoff-focused view
• Underweight BMI Calculator - thinness splits

"Ideal weight" equations (Devine, Robinson, Hamwi) disagree with each other and with the WHO band. Comparison: Healthy weight vs ideal weight.

Children, teens, and pregnancy are not the adult BMI table. Due dates belong on Due Date Calculator, not BMI category labels.

BMR, TDEE, and the third calories number

Three calorie questions, three tools:

1. BMR - energy at rest. BMR Calculator, default Mifflin–St Jeor. Male 80 kg, 180 cm, 30 y → about 1780 kcal/day.
2. TDEE - BMR × activity. Calorie Calculator, same person sedentary ×1.2 → about 2136 kcal/day. Cut/gain lines on that page are planning sketches, not prescriptions.
3. Session burn - MET × kg × hours on Calories Burned Calculator (linked from fitness hub).

Katch–McArdle on BMR needs a body-fat percent you trust - often from tape methods below. Harris–Benedict revised is an alternate regression. None is calorimetry. Illness, thyroid, pregnancy, and eating-disorder recovery need clinicians - not a maintenance TDEE from a weekend web session.

Full accounting rules: BMR vs TDEE vs calories burned. Macro splits from TDEE: Macro calculator split on the fitness side.

Body composition: tape estimates vs scans

BMI Calculator cannot separate fat from muscle. Body Fat Calculator uses circumference equations (US Navy / Hodgdon–Beckett teaching set). You measure neck, waist, hips (female), height, weight - the page returns an estimate with known bias vs hydrostatic weighing or DEXA.

What tape methods do not do:

• Diagnose sarcopenia or eating disorders
• Replace DEXA for research-grade composition
• Clear military or surgery requirements without official standards

Deep comparison: Navy body fat vs DEXA. Lean Body Mass Calculator and Army Body Fat Calculator are related educational views - still not clinical diagnosis.

Workflow: BMI for population screening headline → body fat tape if composition question matters → clinician if metabolic disease is suspected.

Pregnancy: due date is calendar math, not ultrasound

Due Date Calculator applies Naegele's rule: LMP + 280 days (40 weeks), with cycle-length adjustment where the page supports it. That is obstetric dating arithmetic, not crown–rump length from ultrasound, not fetal medicine.

Do not use the due date page to:

• Replace first-trimester ultrasound dating when LMP is uncertain
• Diagnose preterm labor
• Make legal gestational age claims

Article: Due date is Naegele, not an ultrasound. Pregnant adults should not use the adult BMI table as a gestational weight substitute - prenatal charts are clinical.

BAC: educational Widmark, not a breathalyzer or ride plan

BAC Calculator implements a teaching Widmark residual from drinks, weight, sex-based r, hours, and linear elimination β. Default example: 2 US standard drinks, 80 kg, male r=0.68, 2 hours → about 0.0215% BAC. That is worked arithmetic, not your liver tonight.

Never drink and drive. The page cannot decide legal limit, impairment, or safety. Food, medications, tolerance, and drink pacing break the model. Do not time sobriety for keys with a browser.

Full warning: Why not to use a BAC calculator to drive. BAC sits on the wellness hub because it is health education, not training load - same "browser ≠ clearance" rule as BMI.

Screening workflow: from bathroom scale to clinician

A home user can treat wellness tools as a three-step funnel - with hard stops where the clinic takes over.

Step 1 - BMI snapshot
Stand on a scale, measure height once, run BMI Calculator. Read the result as "which WHO band?" not "which disease?" If the band is normal but waist circumference is high, BMI missed central adiposity - that is in Why BMI is not a diagnosis.

Step 2 - composition question (optional)
If you lift, play a contact sport, or your clinician asked about body fat, add Body Fat Calculator tape measurements. Compare trends over weeks, not hours. Tape error from breathing in during neck measure can swing percentages. Not DEXA - see Navy body fat vs DEXA.

Step 3 - energy question (optional, after medical clearance for deficits)
If a registered dietitian or physician already cleared general calorie planning, use BMR Calculator for the rest term, then Calorie Calculator for activity. Never use TDEE output to restrict further during active eating-disorder recovery.

Stop and call a clinician instead of stacking calculators when:

• BMI is in underweight bands and you feel pressured to lose more
• You are pregnant - use obstetric care, not adult BMI labels alone
• You have diabetes, CKD, heart failure, or thyroid symptoms
• You want to know if it is legal or safe to drive after drinking - BAC article, not math

Age, sex, and equation choice on wellness pages

Mifflin–St Jeor on BMR Calculator and Calorie Calculator uses sex as a binary input because the regression data were collected that way. It does not capture hormone therapy, menopause timing, or intersex physiology. Katch–McArdle swaps weight for lean mass if you trust a body-fat estimate - garbage lean mass from a sloppy tape measure produces garbage BMR.

Older adults lose muscle faster than BMI notices - "normal" BMI with sarcopenia is a known clinical pattern. BMI cannot see muscle loss; tape body fat might hint if trends are honest. Neither replaces strength testing or geriatric assessment.

Pediatric BMI percentiles are not on these adult tools. Do not enter a child's height/weight expecting a meaningful category.

Other wellness siblings (quick routing)

Beyond the headline six tools, the wellness category often includes:

• Calorie Calculator - TDEE and rough cut/gain offsets
• Healthy Weight Calculator - WHO normal band in kg
• Ideal Weight Calculator - Devine/Robinson/Miller/Hamwi comparison
• Overweight Calculator / Underweight BMI Calculator - screening views
• Protein Calculator - crosses into nutrition; pairs with fitness macro tools

Unofficial Weight Watchers Points is not WW - legacy formula education only.

When the question becomes 5K pace or 1RM, switch hubs to Fitness Calculators.

Blog cluster map (health posts)

1. Why BMI is not a diagnosis - athletes, age, WHO bands
2. BMR vs TDEE vs calories burned - three calorie jobs
3. Navy body fat vs DEXA - tape limits
4. Healthy weight vs ideal weight - band vs single kg
5. Due date is Naegele, not an ultrasound - LMP dating
6. Why not to use a BAC calculator to drive - Widmark limits

Fitness crossover when training metrics are the real ask: Best fitness calculators, Pace vs speed, Protein grams per kg.

Privacy across wellness tools

Height, weight, LMP dates, drink counts, and circumferences run locally. They are not sent to DevOkk servers to finish BMI or Widmark math. localStorage persistence is convenient on a personal phone, dangerous on a shared clinic kiosk - clear data after use. Site analytics still load per privacy policy; typed health numbers are not required for the formulas.

Do not paste other people's measurements without consent. Do not use BMI or BAC pages to police a partner or child - adult BMI is the wrong table for pediatric screening anyway.

The honest wellness roundup

Open Wellness Calculators when the task is screening, resting energy, tape composition, pregnancy calendar dating, or BAC education - with eyes open about limits.

• BMI - WHO band, not disease name (Why BMI is not a diagnosis)
• BMR / TDEE - regression estimates, not meal plans (BMR vs TDEE)
• Body fat tape - estimate, not DEXA (Navy vs DEXA)
• Due date - Naegele from LMP, not ultrasound (Naegele article)
• BAC - classroom formula, not drive-home clearance (BAC driving article)

The clinic, the obstetric sonographer, the breathalyzer, and the registered dietitian still outrank the browser. The browser beats treating a screening ratio as a diagnosis, or a Widmark percentage as permission to start the car.