Understanding the Devine Formula: How to Calculate Ideal Body Weight (IBW)

If you have ever searched for an "ideal weight" number, you have probably found a formula-based estimate called Ideal Body Weight (IBW). One of the most widely referenced IBW methods in clinical settings is the Devine Formula.

It can be useful as a screening benchmark—especially when paired with other context like body composition, waist measurements, and clinical history. But it is not a diagnosis, and it is not a one-size-fits-all target.

If you want to see your estimate quickly, you can use our Ideal Weight Calculator. The sections below explain what it is doing (and what it is not doing).

The Devine Formula is a simple linear equation that estimates IBW based on height and sex. It was originally developed by Dr. B.J. Devine in 1974 for clinical medication dosing purposes and has since been used as a reference point in healthcare settings.

The key thing to understand: it is not estimating your current body fat percentage, and it does not account for muscle mass, bone density, or body composition. It is an estimate of a reference weight given a height.

The Devine Formula uses a 5-foot baseline and adjusts up or down depending on how far your height is from that point. In practice, you will see it expressed in either inches or centimeters:

A common implementation mistake is to clamp the adjustment at zero—treating anyone under 5 feet as the baseline weight. But mathematically, the Devine Formula allows subtraction for heights under 60 inches (152 cm).

That is why our calculator now allows the "height minus baseline" portion of the equation to go negative for users between 4'0" (122 cm) and 5'0" (152 cm).

For extremely short heights, the formula can produce values that are not physiologically plausible. Rather than showing negative (or near-zero) results, our calculator asks for a minimum height of 4 feet (122 cm) to keep outputs meaningful.

IBW is best viewed as one data point. For a broader baseline, you can also use our BMI Calculator, keeping in mind BMI is also a screening tool with important limitations.

Research indicates that body composition (muscle vs. fat distribution) may be more predictive of health outcomes than total weight alone.

If you want deeper context, our article on understanding body composition explains why the number on the scale is less informative than how that weight is distributed.