BMR Calculator - Basal Metabolic Rate

This BMR calculator is an educational estimate, not medical advice and not a measured metabolic test. Equations from sex, age, height, weight, or an entered body-fat percentage cannot replace indirect calorimetry. Illness, pregnancy, lactation, thyroid disease, medications, eating disorders, and elite sport change resting energy. Private: nothing is uploaded.

A BMR calculator estimates basal metabolic rate: kilocalories per day to sustain vital functions if you stayed at rest in a controlled sense the equations never actually recreate. The default formula is Mifflin–St Jeor. For the default man - 80 kg, 180 cm, 30 years - BMR = 10×80 + 6.25×180 − 5×30 + 5 = 1780 kcal/day. The result panel repeats that check while those inputs remain. This page does not multiply by activity. Sedentary 1.2 through extra 1.9 live on the calorie calculator, where 1780 × 1.2 = 2136 TDEE.

Resting energy is not a lunch plan. It is not RMR from a metabolic cart, not sleeping metabolic rate, and not “calories burned today” from a watch. It is a regression. Two optional equations sit beside Mifflin: Harris–Benedict revised (1984) from weight, height, age, and sex; and Katch–McArdle from lean mass, 370 + 21.6 × LBM_kg. If you type a body-fat percentage, lean mass is weight × (1 − bf/100). A 80 kg person at 20% fat has 64 kg LBM and Katch BMR = 370 + 21.6×64 = 1752.4 kcal/day, close to Mifflin 1780 on this particular body and a coincidence, not a proof they are the same model.

Split 1780 or 2136 into macros on the macro calculator. Protein grams from body weight (not from BMR) belong on the protein calculator. Height and weight without energy still map to the BMI calculator. Lean-mass formulas that do not need a fat percentage (Boer, James, Hume) are on the lean body mass calculator.

1. Choose metric or imperial. Imperial converts to kg and cm before Mifflin or Harris runs.
2. Leave the formula on Mifflin–St Jeor for the 1780 default, or switch to Harris–Benedict, or to Katch–McArdle if you have a body-fat percentage you trust.
3. For Mifflin/Harris enter sex (required), age, height, and weight. For Katch enter weight and body-fat %.
4. Read BMR in kcal/day. Copy if needed. Do not expect a TDEE line - that is intentional. Values stay in this browser up to 30 days and are not uploaded.

Mifflin men on the default: 800 + 1125 − 150 + 5 = 1780. Mifflin women on the same anthropometry: 800 + 1125 − 150 − 161 = 1614. Harris men: 88.362 + 13.397×80 + 4.799×180 − 5.677×30 = 88.362 + 1071.76 + 863.82 − 170.31 = 1853.632. Harris women: 447.593 + 9.247×80 + 3.098×180 − 4.330×30 = 1615.093. The Harris–Mifflin gap on the default man is about 74 kcal at rest, ~89 kcal after a sedentary 1.2 multiply - smaller than most logging error, large enough that you should not shop formulas to justify dessert.

Katch ignores sex and age by construction: it assumes you already isolated lean mass. At 15% fat, 80 kg → LBM 68 kg → BMR = 370 + 1468.8 = 1838.8. At 25% fat, LBM 60 kg → 370 + 1296 = 1666. A ten-point fat error is ~173 kcal. That is why this formula is optional and why a guessed percentage from a social-media photo is worse than Mifflin.

Schofield, Cunningham, and Oxford equations exist in clinical nutrition and are not on this page. Pediatric BMR is a different literature. This tool is an adult planning widget.

Strict BMR protocol: overnight fast, supine, thermoneutral room, no fidgeting. Resting metabolic rate (RMR) is often measured seated after a shorter rest and runs a few percent higher. Consumer calculators blur the words. Mifflin was fitted to resting measurements, not a 4 a.m. BMR suite. Online it is still fair to label the output BMR because that is the search term; it is not fair to claim you measured anything.

TDEE adds everything above rest: sitting, walking, training, fidgeting, and the thermic effect of food in a lump. Taking 1780 as “what I can eat” underfeeds almost everyone who is not bedbound. Use the calorie calculator when you want that next multiply. Do not invent your own 1.0 activity factor unless you are actually at rest all day under medical care.

Popular talk of a “fast metabolism” usually mixes NEAT, muscle mass, and intake underreporting. A 1780 BMR on an 80 kg man is ordinary, not a diagnosis of sluggishness. Thyroid disease is diagnosed with labs and a clinician, not with a web form that came out 50 kcal below a friend’s Harris number.

Female 58 kg, 162 cm, 24 y, Mifflin: 10×58 + 6.25×162 − 5×24 − 161 = 580 + 1012.5 − 120 − 161 = 1311.5 kcal/day.

Male 110 kg, 190 cm, 40 y, Mifflin: 1100 + 1187.5 − 200 + 5 = 2092.5. Harris: 88.362 + 1473.67 + 911.81 − 227.08 ≈ 2246.8.

Female 70 kg, 168 cm, 62 y, Mifflin: 700 + 1050 − 310 − 161 = 1279. Age is the quiet lever: 5 kcal per year on Mifflin.

Katch 90 kg at 18% fat: LBM = 73.8 kg, BMR = 370 + 1594.08 = 1964.08. Same 90 kg at 32% fat: LBM 61.2 kg, BMR = 1691.92. Fat percentage uncertainty dominates Katch more than rounding 6.25×height.

Imperial: 176.4 lb ≈ 80.01 kg, 5 ft 11 in ≈ 180.3 cm, male 30 Mifflin ≈ 1781, essentially the metric demo. Use metric 80 / 180 when you want the exact 1780 check.

After substantial weight loss, measured RMR can sit below prediction for the new smaller body. That is one piece of adaptive thermogenesis. Recalculating Mifflin at the new weight already lowers BMR; biology may lower it more. This page will not apply a starvation correction. Fever, burns, and some cancers raise expenditure; this page will not apply a stress factor either. Those belong in clinical nutrition, not a public form.

Pregnancy is not “female Mifflin plus a snack.” Energy needs rise across trimesters and lactation. Do not use 1614 or 1780 as a prenatal diet. Eating-disorder care often requires intakes far from a predicted BMR, under specialists. If food rules are running your life, a BMR integer is the wrong tool.

Medications and sarcopenia change the relationship between scale weight and metabolically active tissue. A Navy body-fat estimate plus Katch is still an estimate chain - circumference error feeds LBM error feeds BMR error. Prefer consistency over chasing a DEXA-like number from a tape.

Harris–Benedict (1918–19) and the 1984 revision, then Mifflin 1990, then Katch–McArdle from the bodybuilding and research side that wanted lean mass in the equation. Search still asks “what should my BMR be” as if there were a virtuous target. There isn’t. There is a prediction for your inputs. The demonstration value on this site is 1780 kcal/day for the default man so the algebra is inspectable. “Should” is a clinical and personal question this page refuses.

After BMR, daily energy is the calorie calculator; session burn is calories burned; training zones are the target heart rate calculator. This tool only evaluates an adult resting-energy equation and stops.

A metabolic cart estimates energy from oxygen consumption and carbon dioxide production (Weir equation and relatives). That is still an estimate, but it is a measurement of gas exchange, not a rearrangement of 10W + 6.25H. Clinic RMR tests ask you to fast, rest, and avoid caffeine; a fidgety test over-reads. Online Mifflin 1780 cannot see whether you slept four hours or have untreated sleep apnea. If your measured RMR is 1550 and Mifflin says 1780, believe the cart for that morning, then ask why (recent deficit, incomplete rest, machine calibration, or a formula that never fit you).

Cunningham’s lean-mass equation (often cited around 500 + 22 × LBM kg, with variants) is a cousin of Katch–McArdle. This page implements Katch as 370 + 21.6 × LBM because that is the form people type into search boxes. At 64 kg LBM, Katch is 1752.4; a 500 + 22 × 64 Cunningham-style line would be 1908. Different intercepts, same warning: garbage in on body-fat percent, garbage out on kcal. Navy circumference fat on the body fat calculator is convenient and noisy. DEXA is better and still not a chemical cadaver analysis.

Caffeine, nicotine, room temperature, and luteal-phase temperature can move a morning RMR tens of kilocalories. None of those enter Mifflin. Fever and wound healing can move hundreds. This calculator will not apply a “stress factor” of 1.2 for surgery. If you need that, you are in clinical nutrition, not a public TDEE blog post.

Male 75 kg, 178 cm, 33 y, Mifflin: 750 + 1112.5 − 165 + 5 = 1702.5. Harris: 88.362 + 1004.775 + 854.222 − 187.341 ≈ 1760.0. Female 63 kg, 170 cm, 29 y, Mifflin: 630 + 1062.5 − 145 − 161 = 1386.5. Harris: 447.593 + 582.561 + 526.66 − 125.57 ≈ 1431.2. Male 100 kg, 170 cm, 38 y, Mifflin: 1000 + 1062.5 − 190 + 5 = 1877.5 - a shorter heavier adult can out- BMR a taller lighter one because the 10W term dominates the 6.25H term on these numbers.

After a 5 kg loss, the default man at 75 kg, still 180 cm and 30 y, Mifflin becomes 10×75 + 1125 − 150 + 5 = 1730, 50 kcal below 1780. The scale moved more than the formula’s age term would in a decade. Recalculate when mass changes a lot; do not keep 1780 as a souvenir. Adaptive thermogenesis may lower measured RMR beyond those 50 kcal. This page will not invent the extra penalty.

Imperial leftover inches: 5 ft 10 in is 70 in = 177.8 cm, not 180. 5 ft 11 in is 71 in ≈ 180.34 cm, the closer match to the metric demo. 176 lb is 79.83 kg, not 80. Together they still land near 1780, which is why the advertised check is the metric 80 / 180 / 30 case. If you need TDEE after BMR, leave this page and use the calorie calculator rather than multiplying 1.2 in your head and forgetting you did it twice.

Sarcopenic older adults can have a “normal” Mifflin BMR that still overstates metabolically active tissue if weight is mostly fat. Pair with waist, function, and the lean body mass calculator rather than celebrating 1614 as youth. Conversely, a 20-year- old powerlifter’s Mifflin ignores extra muscle; Katch with a decent fat percent is the less-wrong optional path, still not a cart.

Thermic effect of food is often sketched as ~10% of a mixed intake, higher after protein-heavy meals. It is not inside the 1780 Mifflin integer; TDEE multipliers smear it in crudely. Sleeping metabolic rate is usually a bit below daytime RMR. Spontaneous movement (NEAT) is the wild term: two hospital patients with the same predicted BMR can differ by pacing the ward. None of that appears as a checkbox next to Katch. If you want daily energy, leave BMR and open the calorie calculator.

Cold-induced thermogenesis and non-shivering brown-fat talk are real physiology and tiny on most office days compared with mis-picking 1.55 versus 1.2 after you leave this page. Do not add a “ice bath calories” line to 1780. Do not subtract a “slow metabolism personality” either. The demonstration remains male 80 kg, 180 cm, 30 years, Mifflin = 1780 kcal/day, no activity factor.