Normal ideal body weight isn’t a magic number — it’s a BMI-based range, roughly 18.5 to 24.9 for most adults, with side adjustments for muscle, age, and ethnicity. For a 5′4″ woman, that’s about 108 to 145 pounds. Four classic formulas — Hamwi, Devine, Robinson, Miller — spit out 120 to 129 pounds for that same woman. That 9-pound gap is the whole story: formulas were never built to define your health. They were built for drug dosing and quick clinical math. So before you chase a single number, let’s walk through three small tests that separate what matters from what’s noise.

Ideal body weight range infographic: two same-height female silhouettes, one scale showing 120 lbs Hamwi and one scale showing 129 lbs Miller, with text Same Height. Different Math. and healthy range 108–145 lbs

What “normal ideal body weight” actually means

Most people searching that phrase already know roughly where they stand. The question underneath is usually different: “Am I okay at this weight?” A formula doesn’t answer that. A range plus a tape measure does.

The CDC puts healthy adult BMI at 18.5 to under 25, overweight at 25 to under 30, and obesity at 30 or above. Those cutoffs are identical for all adults 20 and older — no age or sex adjustment. The CDC also says plainly that BMI is a screening measure, and should be considered alongside other factors when assessing health.

For a 5′4″ adult, BMI 18.5–24.9 translates to 108–145 pounds. A 37-pound window. The Hamwi formula gives 120. Devine gives about 121. Robinson about 123. Miller about 129. Every one of those numbers sits inside the healthy range. None of them is “more correct” than the range itself.

So Test 1 fails the formula. You don’t need it to know whether you’re in range.

Formula vs. reality: what Hamwi, Devine, Robinson, and Miller actually measure

Now the harder question: even if a formula gave you a number, does that number reflect anything real about your muscle, frame, or fat distribution?

Short answer: no. None of the four formulas included muscle mass, waist circumference, or body fat percentage in their original design. Devine was built for drug dosing — gentamicin pharmacokinetics correlated with ideal body weight, and the equation followed. Hamwi was a clinical quick estimate. Robinson and Miller refined the math but kept the same clinical orientation.

We see the mismatch every week in our own calculator traffic. A reader wrote in last month asking why her Hamwi number was 120 pounds when the healthy range on our adult BMI calculator stretched to 145. She wasn’t confused about the math. She was confused about which number was supposed to be hers. The honest answer: neither. The range is a population band. The formula is a historical artifact. Your waist is the one measurement that actually knows where your fat sits.

If you strength-train regularly, the gap gets wider. A lifter at 5′9″ and 190 pounds reads BMI 28 — overweight on the chart — with 12% body fat. The standard formula has no field for that distinction.

Where does your range need to move?

If the standard 18.5–24.9 band is the starting point, two adjustments move it for large groups of adults. Neither replaces the band. Both shift where the lower-risk zone sits for a specific body.

For Asian adults, the WHO 2004 expert consultation identified further public health action points at 23.0 and 27.5 kg/m², alongside the standard 25 and 30 lines. The consultation noted that Asian populations show different associations between BMI, body fat percentage, and health risk than European populations, and that the proportion at high risk of type 2 diabetes and cardiovascular disease is substantial at BMIs below 25. An Asian BMI calculator applies those lower lines instead of the global table.

For adults over 65, the mortality curve bends the other way. Winter et al’s meta-analysis of 32 prospective cohorts, covering 197,940 adults aged 65 and older, found that using BMI 23.0–23.9 as the reference, mortality risk was 12% higher at BMI 21.0–21.9 and 19% higher at BMI 20.0–20.9. Risk began to increase again above BMI 33.0. Being overweight in the 25–30 band was not associated with increased mortality in this older group. Here’s the practical takeaway: a BMI of 21 at 75 doesn’t give the same reassurance it would for a 35-year-old.

Waist circumference cuts across both adjustments. NHLBI draws the risk line at more than 35 inches for women and more than 40 inches for men. A 5′4″ woman at 140 pounds with a 33-inch waist and a 5′4″ woman at 125 pounds with a 37-inch waist are not in the same risk category, even though both sit inside the BMI window. If the tape and the BMI disagree, the tape usually has the more useful answer.

What to do with all of this

Stop testing whether you match a formula. Test whether your waist stays under the line, whether your weight is stable across seasons, and whether your energy and strength hold up. Those three signals carry more information than any of the four formulas ever could.

If you lift regularly and your BMI reads 28 with a 33-inch waist, the formula is the least useful number on the page. If you are 72 and your BMI is 21, the age-specific mortality data suggest that number deserves a closer look than it would at 35. The range was never the destination. The context is.

So next time you’re staring at a number on a calculator screen, ask yourself: does this actually tell me anything about how I feel or function? Probably not. Your simple tape measure often delivers more useful context than any formula result.

Frequently Asked Questions

What is a normal ideal body weight for a 5′4″ woman?

The BMI-based healthy range is 108–145 pounds. Hamwi gives 120, Devine about 121, Robinson about 123, Miller about 129. All five numbers describe the same height. Only the range accounts for frame, muscle, and fat distribution.

Why do different formulas give different “ideal” weights?

Because they were built for different jobs. Hamwi was a clinical quick estimate. Devine was designed for drug dosing. Robinson and Miller refined the math but kept the clinical orientation. None was built to define a personal health target.

Does normal ideal body weight change with age?

Yes, and the shift is measurable. Winter et al’s 32-cohort meta-analysis found that for adults 65 and older, the reference band was BMI 23.0–23.9. Compared with that reference:

  • BMI 21.0–21.9 carried a 12% higher mortality risk.

  • BMI 20.0–20.9 carried a 19% higher risk.

  • Risk began to increase again above BMI 33.0.

In other words, the lowest-risk zone in that age group sits higher than the standard 18.5–24.9 band.

Should Asian adults use a lower BMI range?

Many clinicians do. WHO’s 2004 consultation identified action points at 23.0 and 27.5 kg/m² for Asian populations because metabolic risk appears at lower BMI values. The practical lower-risk window for many Asian adults runs roughly 18.5–22.9, rather than 18.5–24.9.

What matters more than the formula number?

Waist circumference and trend. NHLBI’s thresholds are more than 35 inches for women and more than 40 inches for men. A stable waist across 6–12 months tells you more than a single formula output. If you want a broader context screen, compare your waist against a healthy weight range for your height rather than chasing one formula output.

Sources

This article is for informational and educational purposes only. It does not constitute medical advice or replace professional health assessment. Always consult a qualified healthcare provider regarding your individual health and weight-related goals. Individual results will vary. The BMI Calculator Blog Team maintains editorial independence and does not sell health products.

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Last updated: October 18, 2026.