Ideal Weight vs. BMI: Which Should You Use?

How ideal body weight formulas and BMI answer different questions, and why neither alone captures overall health.

BMI and ideal body weight are both height-based estimates, but they measure different things and were built for different purposes — using the right one for the right question matters.

What each one actually tells you

• BMI is a ratio (weight ÷ height²) used mainly for broad population-level screening, categorizing results into standard ranges like underweight, healthy, overweight, and obese.
• Ideal body weight estimates an actual target weight in pounds or kilograms, historically developed for medical dosing calculations rather than fitness goals.

What neither one captures

Both are height-and-weight-only estimates that say nothing about muscle mass, bone density, or body fat distribution. A muscular athlete can have a BMI in the "overweight" range or a weight well above their ideal-body-weight estimate while being perfectly healthy — body composition tools like our BMI Calculator (paired with a body fat measurement) give a fuller picture than either number alone.

Try both calculators side by side — the Ideal Body Weight Calculator and the BMI Calculator — to see how they compare for your own height and weight.