How to Calculate Your Ideal Body Weight
Doctors and dietitians don't rely on a single magic number. They combine three simple checks: BMI, frame size, and waist-to-height ratio. Here's the same math, in plain English.
Step 1 — Healthy BMI range
The WHO/CDC defines a healthy adult BMI as 18.5 to 24.9. To convert that to weight:
low_kg = 18.5 × height_m² high_kg = 24.9 × height_m²
Example: a 5'6" (1.68 m) adult has a healthy range of 52 – 70 kg (115 – 155 lbs).
Step 2 — Adjust for gender
Women typically carry a slightly higher body-fat percentage at the same BMI, so they skew toward the lower half of the healthy band. Men skew toward the upper half. Both stay inside 18.5 – 24.9.
Step 3 — Adjust for frame size
Two people of identical height can be equally healthy 10 – 15 lbs apart because of bone structure. Use the wrist-circumference method:
- Small frame: subtract 4% from both ends.
- Medium frame: leave the range as is.
- Large frame: add 4% to both ends.
Step 4 — Waist-to-height ratio
BMI can't see where fat is stored. Central (belly) fat is the dangerous kind. Waist-to-height ratio (WHtR) catches that. The rule: keep your waist under half your height.
Step 5 — Age & muscle mass
After 65, a marginally higher BMI is protective — nudge the range up by ~2%. Athletic or muscular builds also weigh more at the same body-fat percentage; raise the upper bound by 2 – 5%.
Want the math done for you?
The Quick Target Weight calculator runs all five steps in one shot. Slide, tap, done.