Frame Size and Ideal Weight: Does Body Frame Affect Your Goal?

What Is Body Frame Size?

Body frame size refers to the relative size of your bone structure — specifically, how large or small your skeleton is relative to your height. People are typically classified as small, medium, or large frame. A large-framed person has wider, denser bones and can naturally carry more weight than a small-framed person of the same height without that weight being fat.

Frame size gained clinical relevance in the mid-20th century when the Metropolitan Life Insurance Company published ideal weight tables that included frame size adjustments. These tables — and the frame size concept — became widely used in clinical nutrition and dietetics.

How to Determine Body Frame Size: The Wrist Measurement Method

The most widely used method for determining frame size is the wrist circumference method. The wrist is used because it is primarily bone and skin with minimal muscle or fat — making it a good proxy for skeletal size.

How to measure:

1. Wrap a flexible measuring tape around your dominant wrist, just below the wrist bone (the bony prominence on the outside of your wrist).
2. Record the circumference in centimeters.
3. Compare to the table below based on your height.

Frame Size Classification (Wrist Circumference)

Source: Adapted from Metropolitan Life Insurance Company tables and Chumlea WC et al. wrist circumference norms.

How Frame Size Affects Ideal Weight

Traditional frame size adjustments modify the standard ideal weight (typically based on a medium frame) by approximately:

• Small frame: Subtract 10% from the medium-frame ideal weight
• Medium frame: Use the base ideal weight (e.g., from Devine or Robinson formula)
• Large frame: Add 10% to the medium-frame ideal weight

Example — 175 cm man, Devine formula gives 70.5 kg (medium frame):

• Small frame: 70.5 × 0.90 = 63.5 kg
• Medium frame: 70.5 kg
• Large frame: 70.5 × 1.10 = 77.6 kg

This 14 kg spread across the same height illustrates that frame size can meaningfully shift a weight target. Use the Ideal Weight Calculator to see base formula estimates, then apply the ±10% adjustment for your frame.

Limitations of Frame Size Adjustment in Modern Body Composition Science

While frame size adjustment was a reasonable clinical tool in the 1950s–1980s, modern body composition science has largely moved beyond it for several reasons:

1. Imprecise measurement: Wrist circumference is an indirect proxy for skeletal size. Factors like water retention, soft tissue variability, and measurement technique create inconsistency in frame classification.
2. Doesn't account for body fat: A large-framed person can be overweight just as easily as a small-framed person. Frame size adjustment allows for a heavier target weight, but if that extra weight is fat (not bone and muscle), the adjustment is misleading.
3. BMI already captures most of the information: The BMI healthy range (18.5–24.9) gives a 7–8 kg window at any given height. For most people, where you fall within that range already accommodates frame size variation without needing an explicit frame adjustment.
4. Body fat percentage is more direct: Measuring actual body fat % with the BMI Calculator plus body fat percentage assessment gives a more accurate, personalised health picture than any formula that relies only on height and frame size.

The bottom line: Frame size adjustment is a useful sanity check — it explains why a legitimately large-framed person might be healthy at the upper end of the BMI range, even if a formula says they're "overweight." But body fat percentage remains the more actionable and accurate metric for setting real health goals.