VivMetric — Free BMI & Body Fat Calculator

Free BMI Calculator, Body Fat, BMR & TDEE Tools — Built on CDC and WHO Standards

VivMetric is a free collection of health metric calculators built for everyday use in the United States and Canada. Every tool on this page runs locally in your browser, defaults to US imperial units (pounds, inches, ounces), and references the same public health formulas used by the CDC, WHO, NIH, and AASM. There is no signup, no data upload, and no medical advice — just instant calculations you can repeat as often as you need.

The five tools that most visitors come here for are the BMI Calculator, the Body Fat Calculator, the BMR Calculator, the TDEE Calculator, and the healthy weight range readout built into the BMI tool. Together they cover the most common body composition and energy questions people ask their doctor, trainer, or dietitian.

What BMI is and why the CDC uses it

Body Mass Index (BMI) is a weight-to-height ratio. The formula in imperial units is BMI = 703 × weight_lb / height_in², which yields the same number as the metric form kg/m². The CDC adopted the WHO four-category adult classification in the late 1990s: underweight below 18.5, normal 18.5 to 24.9, overweight 25.0 to 29.9, and obese 30.0 and above. The cut-points come from population-level disease risk data, not from any single individual's body composition.

BMI is popular because it needs only a scale and a tape measure. It is also limited for exactly the same reason. Two people with identical BMI can have very different body fat percentages depending on muscularity, age, sex, and ethnicity. A trained lifter may register as "overweight" with very little body fat. An older adult with reduced lean mass may land in the "normal" range while carrying more adipose tissue than is healthy. That gap is exactly why we also publish a dedicated Body Fat Calculator alongside the BMI tool.

Healthy weight range: a practical target, not a verdict

Your healthy weight range is the weight band that keeps your BMI between 18.5 and 24.9 at your height. For a 5 ft 9 in adult that works out to roughly 125 to 168 lb. The number is a screening marker, not a prescription. Doctors use it to flag risk; it does not tell you what you should weigh tomorrow. If you are above the band, a modest 5 to 10 percent weight reduction is associated with measurable improvements in blood pressure, lipids, and glucose tolerance according to NIH guidance. If you are below the band, the focus shifts to preserving lean mass and nutrient intake.

The range also ignores frame size and body composition. A broad-shouldered person will sit near the top of the band; a smaller-framed person may be healthier near the bottom. Use the BMI Calculator above to see your personal range, then cross-check with the body fat tool before drawing any conclusion.

Body fat percentage: a better composition signal than BMI

Body fat percentage estimates the share of your total weight that is adipose tissue rather than lean mass (muscle, bone, organs, water). The Deurenberg formula, used in our calculator, derives body fat from BMI, age, and gender: BF% = 1.2 × BMI + 0.23 × age − 10.8 × gender − 5.4, where gender is 1 for males and 0 for females. It was published in 1991 and validated against hydrostatic weighing.

The American Council on Exercise publishes the reference bands most trainers cite. For men, "fitness" sits at 14 to 17 percent and "acceptable" at 18 to 24 percent. For women, "fitness" is 21 to 24 percent and "acceptable" 25 to 31 percent. Essential fat — the minimum needed for endocrine and structural function — is 2 to 5 percent for men and 10 to 13 percent for women. Going below essential fat is not a goal; it is a clinical concern.

From BMR to TDEE: how many calories you actually burn

Basal Metabolic Rate (BMR) is the energy your body uses at complete rest to keep breathing, circulating blood, and running organs. The Mifflin-St Jeor equation, published in 1990 and now the most widely recommended predictive formula, estimates it from weight, height, age, and gender. For males: BMR = 10×kg + 6.25×cm − 5×age + 5. For females: BMR = 10×kg + 6.25×cm − 5×age − 161. Our BMR Calculator takes pounds and inches and converts internally, so the result is identical to metric input.

TDEE (Total Daily Energy Expenditure) is what most people actually want. It multiplies BMR by an activity factor that folds in the thermic effect of food plus movement. The five standard factors trace back to the 1985 WHO/FAO/UNU expert consultation and were later codified by the US Institute of Medicine in the 2002/2005 Dietary Reference Intakes for Energy:

• Sedentary (×1.200) — little or no deliberate exercise.
• Lightly active (×1.375) — light exercise 1 to 3 days a week.
• Moderately active (×1.550) — moderate exercise 3 to 5 days a week.
• Very active (×1.725) — hard exercise 6 to 7 days a week.
• Extremely active (×1.900) — daily hard training plus a physical job.

The TDEE Calculator shows all five rows at once so you can see the spread. Real TDEE, measured by doubly labeled water, typically falls within 10 to 15 percent of these factorial estimates. Pick the level that matches your typical week, not your best week, and reassess after a month by tracking actual weight change.

How the tools fit together

A sensible workflow runs BMI → body fat → BMR → TDEE. Start with BMI for the population-level screen. Move to body fat percentage to account for composition. Compute BMR for your resting baseline. Finish with TDEE to translate that baseline into a daily calorie target. If weight loss is the goal, a 300 to 500 kcal daily deficit below TDEE is the standard starting point. If weight gain is the goal, eat above TDEE with attention to protein and resistance training to drive lean mass rather than fat.

All formulas on VivMetric are sourced from public health references: CDC adult BMI classification, WHO obesity technical reports, NIH healthy weight guidance, the Mifflin-St Jeor 1990 paper, the Deurenberg 1991 paper, and the IOM Dietary Reference Intakes for Energy. The tools are updated as standards evolve; this page was last reviewed in August 2026. Nothing here is medical advice. For diagnosis or treatment, talk to a licensed healthcare provider.