BMI Goal Weight Calculator

Body Mass Index (BMI) is weight divided by height squared, a single number used to sort adults into broad weight categories. Most calculators run it forward: you enter your weight and get a score. This one runs it backward. You give it a target score and it tells you the weight that produces it, which is the more useful direction when you are setting a goal rather than grading yourself. Add your weight today and it also shows how far away that goal is, and how long a sensible pace would take to get there.

If you only want the healthy band for your height, the Healthy Weight Range Calculator shows that on its own.

Formula:

Goal Weight (kg) = Target BMI × Height² (in meters)
Goal Weight (lbs) = Target BMI × Height² (in inches) ÷ 703

That 703 is the unit conversion folded into a constant, nothing more. The exact figure is 703.07, which is why the two lines can disagree in the second decimal place.

Two sets of category lines

The World Health Organization (WHO) lines are the ones on most charts:

• Underweight: below 18.5 (below 16 is graded severe thinness)
• Healthy: 18.5 up to 25
• Overweight: 25 up to 30
• Obesity class I: 30 up to 35
• Obesity class II: 35 up to 40
• Obesity class III: 40 and above

Charts usually write the healthy band as “18.5 to 24.9”. That is the top of the band written to one decimal place, not a separate line, so this calculator uses 25, the same as the main BMI calculator.

In the UK, NICE (the National Institute for Health and Care Excellence) uses lower lines for adults of South Asian, Chinese, other Asian, Middle Eastern, Black African or African-Caribbean family background. Diabetes and heart disease risk starts at a lower BMI in those groups, so overweight begins at 23 and obesity at 27.5, and the higher obesity classes are usually taken 2.5 lower as well. Pick that option and the healthy range, the verdict and the chart all follow it.

Worked example

Someone 5'8" tall (68 inches, 1.7272 m) wants to reach a BMI of 22.
Height squared: 1.7272² = 2.9832 m²
Goal weight: 22 × 2.9832 = 65.6 kg (144.7 lbs)
Imperial check: 22 × 4,624 ÷ 703 = 144.7 lbs
Healthy range: 18.5 × 2.9832 = 55.2 kg (121.7 lbs) up to 25 × 2.9832 = 74.6 kg (164.4 lbs)
On the NICE lower lines the healthy band stops at 23 instead, which is 68.6 kg (151.3 lbs).

They weigh 190 lbs today, a BMI of 28.9. Reaching 144.7 lbs means losing 45.3 lbs, and at 1 to 2 lbs a week that is 23 to 46 weeks, roughly five to eleven months.

The pace matters more than the target

The CDC (Centers for Disease Control and Prevention) puts a steady pace at about 1 to 2 pounds a week, which is 0.5 to 1 kg, because people who lose weight at that rate are more likely to keep it off. A 45-pound goal that looks like a summer project is closer to a year’s work. Planning for that from the start is what stops it turning into a crash diet in month two.

The goal does not have to be the finish line either. The CDC also notes that losing 5 to 10% of your body weight usually improves blood pressure, cholesterol and blood sugar, so for someone at 190 lbs the first 10 to 19 lbs already count.

Limits

BMI is a screening tool, not a diagnosis. It cannot tell muscle from fat, so a lifter and a sedentary person of the same height and weight get the same score. In January 2025 a commission convened by The Lancet Diabetes & Endocrinology went further and said BMI alone should not be used to diagnose obesity: it needs confirming with a waist measurement or a direct body fat measurement. A waist-to-height ratio under 0.5 is the quickest second check, and it needs one tape measure.

Adult categories do not apply to children and teens, who are measured against percentile charts, or during pregnancy.