BMR vs TDEE vs Calories Burned: Three Numbers, Three Jobs

DevOkk splits the jobs on purpose. BMR Calculator stops at the basal estimate (default Mifflin–St Jeor). Calorie Calculator multiplies by activity and shows rough cut/gain offsets. Calories Burned Calculator is Compendium-style METs for one activity block. All three run in the browser. None is medical advice. None of them is a meal plan.

BMI is a different instrument entirely: Why BMI is not a diagnosis. Composition is Navy body fat vs DEXA.

BMR is rest, not a lifestyle

Basal metabolic rate tries to answer: if you stayed in bed, how much energy would the organs and the temperature regulation cost. You cannot measure that with a phone. Clinical research uses calorimetry. Online tools use regression equations from height, weight, age, and sex - or lean mass if you pick Katch–McArdle.

DevOkk’s default is Mifflin–St Jeor:

• Male: 10×kg + 6.25×cm − 5×age + 5
• Female: 10×kg + 6.25×cm − 5×age − 161

Male, 80 kg, 180 cm, 30 years: 800 + 1125 − 150 + 5 = 1780 kcal/day. That is the sample on the BMR page. It is not “what you burned at your desk job.” It is not “what you should eat.” It is the resting term other formulas will multiply.

Harris–Benedict revised is the older pair of equations you still see in textbooks. For the same person it will not match 1780 exactly. That disagreement is normal. The equations were fit on different samples. Pick one and keep it for comparison week to week. Do not rotate equations until you like the larger number.

Katch–McArdle is 370 + 21.6 × lean mass (kg). Lean mass comes from a body-fat percentage. If that percentage came from a bathroom scale’s mystery impedance, you have stacked two estimates. Navy tape is still not DEXA. Only use Katch if you have a composition number you are willing to stand behind.

TDEE is BMR times a coarse activity factor

Calorie Calculator takes the same Mifflin default and multiplies. Sedentary is commonly ×1.2. 1780 × 1.2 = 2136 kcal/day. That is the sample TDEE on the page. “Lightly active,” “moderate,” and “very active” are not accelerometer readings. They are buckets. People over-file themselves as very active because they went to the gym three times and sat the rest of the week.

If you already multiply by “very active,” you have claimed a lot of movement in the daily total. Logging every MET session on top of that is double-counting. The cleaner pattern:

• Desk job, 3 gym sessions: sedentary or light TDEE, then add sessions with the MET tool or bump one activity rung - not both at full strength.
• Manual labor all day: a higher factor, and do not add “work” again as a MET block unless the factor was truly sedentary.

Cut and gain rows on the calorie page are arithmetic offsets from TDEE (often ±500 kcal as a teaching device). They are not a rate of fat loss you can promise. Water, glycogen, and a bad week of sleep move the scale more than the spreadsheet. Illness and medication change expenditure. The page says planning estimate. Believe that sentence.

Calories burned is one session, not the day

METs (metabolic equivalents) compare an activity to sitting rest, defined as 3.5 mL O₂/kg/min in the teaching version. Energy for a block is roughly MET × mass(kg) × hours, then converted to kilocalories. Calories Burned Calculator ships presets such as walking 3.5, easy jog 7, running about 6 mph (9.8), moderate cycling 7.5, swimming 6, strength 6, yoga 2.5, plus a custom MET box.

Those numbers are Compendium-style averages. Fitness, grade, rest between sets, outdoor wind, and whether you actually ran 6 mph vs jogged 5 all move the true cost. A 70 kg person at MET 9.8 for 30 minutes is not the same engine as a 90 kg person. The formula scales with mass; it still is not your VO₂.

Strength training is especially noisy. The Compendium MET for “resistance” does not know your rest intervals or your drop sets. Treat the output as order-of-magnitude, not as a receipt to eat back.

Heart-rate watches that emit a custom number are a different product. DevOkk does not ingest your wearable. Target Heart Rate Calculator is 220−age and Karvonen zones - also estimates, and a fitness-page topic, not a calorimeter.

A worked desk-and-run example without stacking

Same adult as the tool defaults: male, 80 kg, 180 cm, 30 years.

1. BMR Mifflin = 1780 kcal.
2. If the day is mostly sitting, TDEE sedentary ≈ 2136 kcal. That 356 kcal gap is the activity factor trying to cover fidgeting, walking to the kitchen, and ordinary standing - not a 10K.
3. A 30-minute easy jog at MET 7: 7 × 80 kg × 0.5 h ≈ 280 kcal on the MET page.

If you keep TDEE at 2136 and add 280, you have counted some of the day’s movement twice unless you had chosen a truly basal TDEE (which humans do not live). If you set TDEE to “very active” because of that jog, you have probably overshot. One honest sketch: sedentary TDEE plus the MET session, or a light/moderate TDEE and no extra MET, then compare weekly average weight - not daily panic.

This is still not a diet. A registered dietitian uses more than three form fields.

Activity factors are buckets, not Fitbit exports

The usual adult multipliers you see on TDEE pages are teaching rungs:

• Sedentary ≈ ×1.2 - desk, little structured training
• Light ≈ ×1.375 - light exercise a few days a week
• Moderate ≈ ×1.55
• Very active ≈ ×1.725
• Extra ≈ ×1.9 - physical job plus training (easy to over-claim)

Those coefficients came from older activity classifications, not from your watch’s active-calorie tile. If you sit eight hours, commute seated, and lift three times, “very active” is usually a vanity rung. The MET tool is then the right place to price those three sessions - or you bump one rung, not both.

A week of 2136 × 7 = 14952 kcal of sedentary TDEE is a sketch of weekly energy. One 280 kcal jog is 2% of that week. Treating every jog as a license to add a 600 kcal dessert is the spreadsheet failure mode, not a rounding error in Mifflin.

Harris–Benedict will not match Mifflin, and that is expected

Harris–Benedict revised (male) is a different regression: 88.362 + 13.397×kg + 4.799×cm − 5.677×age, in the common restatement. For 80 kg, 180 cm, 30 years that is not 1780. You will get a different basal, then a different TDEE after the same ×1.2. Switching equations every Monday to chase a larger TDEE is not “finding the accurate one.” It is overfitting a number you never measured.

Keep Mifflin as the DevOkk default if you want a single line to compare month to month. Use Harris only if a textbook problem named it. Use Katch only with a fat percentage you would defend to a coach who owns a DEXA, not a scale that beeped.

Why the numbers disagree with a wearable

Wearables estimate from heart rate, motion, and a proprietary model. Mifflin estimates from four anthropometric fields. METs estimate from a table. They will not match. That is not a bug in DevOkk. It is three models of an unmeasured quantity.

If you need them to line up, you are asking for calorimetry. A consumer site will not provide it. Use one method for trend, not three methods for a courtroom.

Illness, age, and the equations’ silence

Fever, recovery from surgery, pregnancy, lactation, hyperthyroidism, and some cancers change expenditure. None of the three DevOkk pages asks about those states in a way that makes the output clinical. Older adults can lose muscle; Mifflin still sees weight and height. Adaptive thermogenesis after a long deficit is real and not in the activity dropdown.

If a clinician set a target, use that target. An online TDEE is not a second opinion.

Protein and macros are a later split

Once you have a calorie sketch you trust enough to plan with, grams of protein, carbohydrate, and fat are a different calculator family: Macro Calculator, Protein Calculator, Carbohydrate Calculator, Fat Intake Calculator. Those pages still start from calories you typed. Garbage TDEE in, garbage macros out. They belong with fitness nutrition, not with the BMR definition.

Weight Watchers–style points are another overlay entirely and are unofficial on DevOkk. Do not mix WW points with TDEE as if they were SI units.

Privacy and the shared laptop

BMR, TDEE, and MET math run locally. Weight and age are not uploaded to finish the formula. localStorage can remember the last inputs on that browser. Clear them. Analytics still load. Local does not mean “this is my metabolic ward result.”

Do not enter someone else’s weight to “prove” they overeat. The ethics problem is older than JavaScript.

Three calorie numbers, three jobs

Open BMR Calculator when the question is the resting term. Open Calorie Calculator when you want that term times a coarse daily activity factor. Open Calories Burned Calculator when the question is one activity block in MET units. Write down which system you used. Do not add all three and call it science. The meal plan, if you need one, is a human with a license - not the sum of three browser tabs.