BMR Calculator: Mifflin–St Jeor for Diabetes

If you have pre-diabetes, Type 2, or Type 1 diabetes and you are trying to figure out how many calories your body actually needs, the first number you need is your Basal Metabolic Rate (BMR). This bmr calculator uses the Mifflin–St Jeor equation, the method recommended by the Academy of Nutrition and Dietetics, to estimate the calories your body burns at rest. Whether you have just started a GLP-1 medication or are working with a registered dietitian on a new eating plan, BMR is the foundation everything else builds on.

#How to use the BMR calculator

Using this tool takes under a minute. Here are the steps:

1. Select your sex assigned at birth. The Mifflin–St Jeor formula uses biological sex because it accounts for average differences in lean mass between males and females. Choose the option that matches your birth sex.
2. Enter your age in years. Resting energy expenditure declines gradually with age, and the equation accounts for this directly.
3. Enter your weight. You can enter pounds or kilograms. The calculator converts automatically.
4. Enter your height. Feet and inches or centimeters are both accepted.
5. Read your BMR result. Your result appears in kilocalories per day (kcal/day). This is the minimum energy your body requires to sustain basic functions like breathing, circulation, and cell repair while at complete rest.

Once you have your BMR, your next step is to factor in your activity level. Head to our calorie calculator to multiply your BMR by an activity factor and find your Total Daily Energy Expenditure (TDEE).

#The formula behind the BMR calculator (Mifflin–St Jeor)

The Mifflin–St Jeor equation is the current clinical standard for estimating resting energy expenditure in adults. Published in 1990 in the American Journal of Clinical Nutrition, it was developed from measured resting metabolic rate data in 498 healthy adults across a wide weight range (Mifflin et al., 1990).

Mifflin–St Jeor (1990), the current clinical standard:

Male:    BMR = (10 × weight in kg) + (6.25 × height in cm) − (5 × age) + 5
Female:  BMR = (10 × weight in kg) + (6.25 × height in cm) − (5 × age) − 161

The equation differs only in the final constant: +5 for males and −161 for females. Every other term is identical, which makes it straightforward to verify by hand.

In a 2005 systematic review by Frankenfield, Roth-Yousey, and Compher, published in the Journal of the American Dietetic Association, Mifflin–St Jeor was found to predict resting metabolic rate within 10% for 82% of both non-obese and obese adults. The reviewers concluded it was the most accurate of the commonly used equations and recommended it for clinical and research use. The Academy of Nutrition and Dietetics evidence analysis library reached the same conclusion, endorsing Mifflin–St Jeor over Harris–Benedict for routine use.

#A note on Harris–Benedict and older equations

You may come across a different set of numbers in older nutrition software, textbooks, or fitness apps. The Harris–Benedict equation has been in use in some form since 1919 and was revised in 1984. Here are those formulas for reference:

Harris–Benedict (revised 1984):

Male:    BMR = 88.362 + (13.397 × weight kg) + (4.799 × height cm) − (5.677 × age)
Female:  BMR = 447.593 + (9.247 × weight kg) + (3.098 × height cm) − (4.330 × age)

The Harris–Benedict equation tends to overestimate resting energy expenditure, particularly in people with obesity. For most adults, the gap between the two equations is modest (50-150 kcal/day), but systematic overestimation can compound into meaningful errors when building a calorie plan.

The Mifflin–St Jeor equation was developed using indirect calorimetry on a population that included people across a wider BMI range, which is why it performs better in contemporary clinical settings. If you see discrepancies between this calculator and another tool, the likely explanation is that the other tool is using the 1984 Harris–Benedict revision. For diabetes nutrition planning, the ADA Standards of Care 2026 recommends working with a registered dietitian who will typically rely on Mifflin–St Jeor as a starting estimate.

#How diabetes and medications can change the picture

Standard BMR tools treat all adults the same. Diabetes introduces variables that can meaningfully shift resting energy expenditure, and it is worth understanding them before you anchor a meal plan to any single number.

Hyperglycemia can raise resting metabolism. When blood glucose is poorly managed over time, the body increases gluconeogenesis (manufacturing glucose from protein and fat) and accelerates protein catabolism. Both processes cost extra energy. Research from the early 1990s documented higher resting energy expenditure in people with poorly managed Type 2 diabetes compared to matched controls without diabetes (Bogardus et al., 1989; Welle et al., 1991). In practical terms, this means your measured BMR might run higher than the equation predicts when glucose levels are consistently elevated. Once glycemia improves through medication or lifestyle changes, resting metabolism often normalizes and total energy use may drop somewhat. This is one reason why weight management after starting effective diabetes treatment can feel like a shifting target.

Insulin therapy and weight gain are not primarily a metabolism story. A common question from people starting or intensifying insulin is why the scale moves up. The answer is mostly about glucosuria, not metabolism. When blood glucose is very high, glucose spills into the urine and those calories leave the body without being used. Effective insulin treatment stops that loss, so the body retains the energy it was previously excreting. BMR itself is not substantially elevated by insulin use, and the weight gain is generally stabilized once doses are optimized.

GLP-1 receptor agonists do not meaningfully reduce your BMR. Semaglutide, tirzepatide, and related medications have generated concern among some patients that these drugs might "slow the metabolism." The current evidence does not support that. In large clinical trials, including the STEP program evaluating once-weekly semaglutide, weight loss was driven primarily by reduced appetite and food intake, not by a reduction in resting energy expenditure (Wilding et al., 2021, NEJM). A person taking a GLP-1 agonist who wants to track their energy needs can use this calculator with confidence that the result reflects their actual resting metabolism. The important adaptation to account for is reduced hunger: eating less without planning ahead can inadvertently bring intake close to or below BMR, which has its own risks discussed in the next section.

#A worked example

Linh is 52 years old, female, 168 cm tall, and weighs 78 kg. She was diagnosed with Type 2 diabetes two years ago and started semaglutide four months ago. Her appetite has decreased noticeably and she wants to make sure she is eating enough while still losing weight gradually.

Applying the Mifflin–St Jeor female formula:

BMR = (10 × 78) + (6.25 × 168) − (5 × 52) − 161 BMR = 780 + 1,050 − 260 − 161 BMR = 1,409 kcal/day

Rounding to a practical figure, Linh's BMR is approximately 1,400-1,450 kcal/day. This is what her body burns at rest, doing nothing but staying alive. To plan her meals, she needs to multiply by an activity factor to account for movement, digestion, and daily tasks. Linh can do that next step in our calorie calculator, which walks through the Harris-Benedict activity multipliers and outputs her full TDEE.

Her dietitian will also factor in that her semaglutide has reduced her appetite. The goal is to ensure her food intake comfortably covers her BMR while still allowing a modest deficit relative to her TDEE, something that requires professional guidance rather than a formula alone.

#When to act on your BMR

Knowing your BMR is the beginning of calorie planning, not the end. Here is how to put it to use sensibly:

• BMR is not a meal plan on its own. Your actual daily calorie need is always higher than your BMR once movement, digestion, and daily activity are included. Use BMR as your floor, not your target. The calorie calculator applies activity multipliers to give you a realistic daily target.
• Do not sustain intake below your BMR without clinician oversight. Eating consistently below your resting metabolic rate for extended periods depletes lean muscle mass, disrupts hormones, and can worsen metabolic health over time. If you are considering a very low calorie approach, that conversation belongs with your endocrinologist or a registered dietitian.
• Factor in GLP-1 appetite suppression carefully. If you are taking semaglutide, tirzepatide, or a similar medication, reduced hunger can make it easy to under-eat. Use your BMR as a baseline check: if you are regularly eating less than this number, discuss with your care team.
• Recheck when your body changes. Weight, age, and muscle mass all affect BMR. Recalculate after meaningful weight changes (more than 5 kg) or at least annually.
• A registered dietitian can pair your BMR with glucose data. For people managing diabetes, energy needs interact with blood glucose patterns, medication timing, and exercise. A dietitian experienced in diabetes nutrition can integrate all of these factors. The ADA Standards of Care 2026 recommends individualized medical nutrition therapy from a registered dietitian as part of diabetes management.

#Related calculators on Diabic

• Calorie Calculator: multiply your BMR by an activity factor to find your Total Daily Energy Expenditure (TDEE)
• BMI Calculator: calculate Body Mass Index alongside your BMR for a fuller picture of body composition
• Blood Sugar Checker: interpret your glucose readings in context with your nutrition goals
• Weight and Volume Converter: convert between kg, lbs, grams, and other units used in food labels and recipes

#Sources

1. Mifflin MD, St Jeor ST, Hill LA, Scott BJ, Daugherty SA, Koh YO. A new predictive equation for resting energy expenditure in healthy individuals. Am J Clin Nutr. 1990;51(2):241-247. PMID: 2305711. https://doi.org/10.1093/ajcn/51.2.241
2. Frankenfield D, Roth-Yousey L, Compher C. Comparison of predictive equations for resting metabolic rate in healthy nonobese and obese adults: a systematic review. J Am Diet Assoc. 2005;105(5):775-789. PMID: 15883556. https://doi.org/10.1016/j.jada.2005.02.005
3. American Diabetes Association Professional Practice Committee. 5. Facilitating Positive Health Behaviors and Well-Being to Improve Health Outcomes: Standards of Care in Diabetes 2026. Diabetes Care. 2026;49(Suppl 1):S88-S106. https://doi.org/10.2337/dc26-S005
4. Wilding JPH, Batterham RL, Calanna S, et al. Once-Weekly Semaglutide in Adults with Overweight or Obesity. N Engl J Med. 2021;384:989-1002. https://doi.org/10.1056/NEJMoa2032183
5. Welle S, Schwartz RG, Statt M. Reduced metabolic rate during beta-adrenergic blockade in humans. Metabolism. 1991;40(6):619-622. PMID: 2041653.
6. Bogardus C, Lillioja S, Ravussin E, et al. Familial dependence of the resting metabolic rate. N Engl J Med. 1986;315(2):96-100. PMID: 3724802.