Health Calculators

Not reliably. BMI can't tell muscle from fat, and muscle is denser, so people who strength-train regularly often land in the overweight category despite having low body fat. Body fat percentage or waist-to-height ratio reads muscular bodies more accurately than BMI alone.

BMR is the calories your body burns at complete rest just to keep functioning. TDEE takes that number and scales it up with an activity multiplier to include walking, working, exercising, and digesting food. TDEE is always the larger figure and the one to use when planning daily intake.

A common, sustainable starting point is 300 to 500 calories below your TDEE per day, which tends to produce gradual, muscle-sparing loss for most people. Cutting much further raises the risk of losing lean muscle along with fat. Recalculate every 10 to 15 pounds lost, since a lower body weight also lowers both BMR and TDEE.

For most adults, a BMI between 18.5 and 24.9 is classified as the healthy weight range, with below 18.5 as underweight, 25 to 29.9 as overweight, and 30 or above as obesity. These thresholds are the same for adult men and women but are interpreted differently for children and teens, and several health bodies use lower cutoffs for Asian populations.

No. Children and teens are measured against BMI-for-age percentile charts specific to their sex, since normal body composition changes constantly as kids grow. The fixed 18.5-to-24.9 healthy range used for adults doesn't apply to a young person's number.

Not the same way you would outside pregnancy. The standard adult BMI bands on this page aren't meant to be rechecked week to week once you're pregnant. Instead, your pre-pregnancy BMI is the starting point clinicians use to set a total pregnancy weight-gain target: national guidance recommends roughly 28-40 lbs of total gain for a pre-pregnancy BMI under 18.5, 25-35 lbs for 18.5-24.9, 15-25 lbs for 25-29.9, and 11-20 lbs for 30 and above. Use this calculator once, before pregnancy or early on, then follow a prenatal care provider's tracking from there.

Day-to-day weight swings are usually water, not fat. Cleveland Clinic notes a normal daily fluctuation of about 2-3 pounds in either direction is common even at a stable weight, driven by sodium intake, carbohydrate stored as glycogen, digestion, and hormonal shifts rather than real fat gain or loss. Since both calculators use whatever weight you enter, a single day's fluctuation can nudge the result slightly. Weighing at a similar time of day and watching the trend over 2-3 weeks is more reliable than any single reading.

No, this calculator estimates maintenance calories for a non-pregnant, non-lactating adult and doesn't add anything on top for those cases. The NIH's Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD) states that breastfeeding increases caloric need by about 450 to 500 calories per day above pre-pregnancy levels. Pregnancy needs also increase and vary by trimester. Both situations call for a provider's or dietitian's guidance rather than this calculator's default output.

Every calculator publishes its formula in plain English and a worked example. That example is a test case: the build re-derives it against the live calculation and fails if the two disagree, so the number explained on the page is provably the number the tool produces.

Any value that is not pure arithmetic — a threshold, a rate, a conversion factor — is cited to its original source with a retrieval date. Rates change, so check the "last updated" date and the linked source for anything time-sensitive.