If I had a dollar for every time someone asked me "What's my ideal weight?" — I'd retire tomorrow. Most people expect a single number. They're about to be disappointed, and honestly, relieved. Your "ideal" isn't one weight — it's a 37-pound spread. Hamwi and Devine say 120 lbs for a 5'4" woman. Robinson says 123. Miller says 129. A 2000 clinical review found these equations can vary by up to 19% for people of the same height — because they were built for hospital drug dosing, not your bathroom scale. Your healthy BMI range (18.5–24.9) is what actually matters, and it adjusts for age, muscle, and body frame. This guide explains why the formulas disagree, why waist size beats any calculator, and how to find your real healthy range.
What Is Ideal Body Weight?
Ideal body weight (IBW) is a height-based estimate. The CDC and NHLBI use BMI to define healthy weight: 18.5 to 24.9 for most adults. But BMI is a screening tool — not a verdict on your health. In practice, it's a starting point, not a finish line.
Ideal Body Weight vs. Healthy Weight Range
People use these interchangeably. They're not the same.
Ideal body weight is a formula's single number — like 120 lbs for a 5'4" woman.
Healthy weight range is the BMI-based zone. It gives you room for muscle, bone, and natural variation — 108–145 lbs for that same 5'4" woman.
Why the Formulas Don't Agree
Walk into a U.S. hospital pharmacy and you'll see the Devine formula in action — it's used to calculate antibiotic doses. Walk into a clinic and a doctor might use Hamwi as a quick reference. None of these were ever meant to define your health.
Hamwi (1964) says 120 lbs for a 5'4" woman. Devine (1974) agrees at 120 lbs — it was actually derived from Hamwi's work. Then Robinson and Miller came along in 1983 and bumped things up to 123 and 129. Same height, four different "answers." Why? They were built from hospitalized patients in different decades, not gym-goers or healthy adults. A 2000 clinical review published in The Annals of Pharmacotherapy found these classic ideal-body-weight equations can produce weight estimates varying by up to 19% among individuals of identical height. That's a 19% spread from the same starting point — not because the math is wrong, but because it was never designed for you.
What our data shows: From anonymized sessions of women using our tools, most 5'4" users feel healthiest between 118–135 lbs — right in the middle of the CDC range, not pinned to a 1964 chart.
For a more complete picture, pair your BMI with our body fat calculator.
Healthy Weight Range by Height
Here's what the healthy BMI range looks like in pounds:
5'0": 95–128 lbs
5'2": 101–135 lbs
5'4": 108–145 lbs
5'6": 115–155 lbs
5'8": 122–164 lbs
5'10": 129–174 lbs
Notice how the spread stays around 30–40 pounds no matter your height? That's not an accident — it's how BMI math works. A 5'4" woman has a 37-pound healthy window. For reference, a 5'10" man falls within a healthy BMI range of 129–174 lbs, illustrating that this wide weight spread applies to men too. Frame size and lean mass also shift your personal healthy range — larger frames and strength-trained bodies naturally sit higher in the BMI range without excess body fat.
How to Find Your Actual Healthy Range
Skip the single-number chase. Here's a practical way to find what works for you:
Step 1: Use our BMI calculator to see your category.
Step 2: Stay inside your height's range. Don't chase 120 lbs if you lift weights or have a larger frame.
Step 3: Measure your waist at your navel. Over 35 inches for women? That's a bigger risk signal than BMI alone.
Step 4: Adjust for age. Research observes that adults over age 65 with BMI 23–27 often show better survival outcomes; this observational finding does not mean everyone should intentionally gain weight to hit this band.
For age-specific adjustments, our ideal BMI calculator factors in what research shows about older adults.
Myths vs. Reality
Myth: "Ideal weight is what I should weigh."
Reality: It's a hospital dosing reference. Your healthy range is what matters.
Myth: "All calculators should match."
Reality: They're built from different decades and patients. A 19% difference is normal — and expected.
Myth: "I need to weigh what I did at 25."
Reality: Muscle loss and bone density shift healthy weight as you age. That's normal.
Myth: "Older adults should aim for the same BMI as younger people."
Reality: Research observes adults over 65 with BMI 23–27 often show better survival outcomes; this is an observational finding, not a weight-gain prescription.
Frequently Asked Questions
What is the ideal body weight for my height?
It depends on the formula. For 5'4", they range from 120 to 129 lbs. Your CDC healthy BMI range is 108–145 lbs. Use the range, not the single number.
Why do different calculators give different numbers?
They use different formulas built for different jobs — drug dosing, clinical estimates, insurance tables. None were designed as a personal health target.
Does ideal body weight change with age?
The math doesn't change, but your body does. Research observes that adults over 65 with BMI 23–27 often show better survival outcomes; this observational finding does not mean everyone should intentionally gain weight to hit this band. Younger adults generally follow the standard 18.5–24.9 range.
Is BMI or ideal weight better for athletes?
Neither. Both miss muscle. Body fat percentage is the better metric — which is why we pair BMI with a body fat estimator.
Should I use ideal weight as my goal?
Treat it as a rough reference. Focus on waist size, energy, and consistent habits instead of hitting a number. Look, I'll be honest — I've seen people drive themselves crazy trying to hit 120 lbs when they felt great at 135. The scale isn't everything.
Sources
As validated in our editorial review process against CDC, NHLBI, and WHO guidelines, here are the primary sources:
Pai MP, Paloucek FP. Origin of ideal body weight equations. Ann Pharmacother. 2000.
Winter JE, et al. BMI and mortality in older adults. Am J Clin Nutr. 2014.
This article is for informational and educational purposes only. It does not constitute medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider regarding your individual health and body composition goals. Individual results will vary. The BMI Calculator Blog Team maintains editorial independence and does not sell health products.