Ideal Body Weight Worked Examples: Six Devine Formula Calculations, Shown in Full
Six fully worked ideal body weight examples — men, women, below-five-feet, BMI cross-checks, and adjusted body weight — with every step of the Devine arithmetic on the page.
The Devine formula is three lines of arithmetic, which makes it the rare health calculation you can fully verify by hand. This post walks six realistic cases through an ideal body weight calculator's exact math: two men, two women, a height below five feet, a BMI cross-check, and an adjusted-body-weight computation of the kind nurses actually perform. Every step is shown — inches over five feet, kilograms gained, pounds converted — so you can check each line with a phone calculator. As throughout, these are educational estimates from a dosing formula, not targets or medical advice; the goal is numeracy, not judgment.
CHAPTER 01The Formula Recap
Two lines cover everything. Devine for men: 50 kilograms plus 2.3 kilograms for every inch over five feet. Devine for women: 45.5 kilograms plus 2.3 kilograms per inch over five feet. Conversions use 1 kilogram equals about 2.205 pounds. Below five feet, subtract 2.3 kilograms per inch under, with the caveat that the formula was fitted on average-height adults and is least trustworthy at short heights.
Adjusted body weight, used in dosing when actual weight far exceeds ideal, is the third line: IBW plus 0.4 times the difference between actual and ideal. Keep those three lines in view and every example below is checkable in under a minute — which is the whole point of showing the work. The same arithmetic runs inside /ideal-body-weight-calculator.html, so every result here can be reproduced there in seconds.
A note on precision before the examples: the formula itself is exact — 2.3 kilograms per inch is a definition, not a measurement — so the only uncertainty lives in which formula a tool implements and how it rounds. Hand computation and a well-built calculator should agree to the tenth of a kilogram; if they do not, the tool's base constant or conversion factor is the suspect, not your arithmetic. That is the quiet superpower of a formula this simple: disagreements have addresses.
CHAPTER 02Example 1: A Man Who Is 5 Feet 10 Inches
Height above five feet: 10 inches. IBW equals 50 plus 10 times 2.3. Ten times 2.3 is 23, so IBW is 73.0 kilograms.
Convert to pounds: 73.0 times 2.205 is 160.965, so about 161 pounds.
Interpretation: 73 kilograms is the textbook Devine estimate for this height, and it is deliberately lean — a weight near a BMI of about 22.9 for this frame. Note what the number did not consider: muscle, age, health. It is a reference point, and nothing more.
CHAPTER 03Example 2: A Woman Who Is 5 Feet 4 Inches
Height above five feet: 4 inches. IBW equals 45.5 plus 4 times 2.3. Four times 2.3 is 9.2, so IBW is 54.7 kilograms.
Convert: 54.7 times 2.205 is 120.6, so about 121 pounds.
Interpretation: the female base is 4.5 kilograms lighter than the male base, and this example shows the whole difference at a modest height. A woman of this height in the middle of the normal BMI band commonly weighs somewhat more than 54.7 kilograms — which is fine, and is exactly why 'ideal' needs its quotation marks.
CHAPTER 04Example 3: A Man Who Is 6 Feet 2 Inches
Height above five feet: 14 inches. IBW equals 50 plus 14 times 2.3. Fourteen times 2.3 is 32.2, so IBW is 82.2 kilograms.
Convert: 82.2 times 2.205 is 181.25, so about 181 pounds.
Interpretation: notice the formula's linearity — each extra inch is worth exactly 2.3 kilograms forever. Real physiology is not that tidy at tall heights, which is one reason competing formulas disagree more the taller the person. The estimate is still the dosing convention, so it remains what most calculators print.
CHAPTER 05Example 4: A Woman Who Is 4 Feet 11 Inches
Height below five feet: 1 inch. IBW equals 45.5 minus 1 times 2.3, which is 45.5 minus 2.3 — so 43.2 kilograms.
Convert: 43.2 times 2.205 is 95.3, so about 95 pounds.
Interpretation: this is the formula's least comfortable case, and the caveat is the lesson. Devine was fitted on average-height adults; at short heights the linear subtraction is an extrapolation, and some implementations refuse to go below the five-foot base at all. Treat 43.2 kilograms as an arithmetic answer, not a settled one.
CHAPTER 06Example 5: BMI Cross-Check — 5 Feet 9 Inches, 77 Kilograms
IBW first: 9 inches over five feet, so 50 plus 9 times 2.3 equals 50 plus 20.7 — that is 70.7 kilograms, about 155.9 pounds.
Now BMI, which needs metric: 5 feet 9 inches is 69 inches, or 175.3 centimeters — 1.753 meters. BMI equals weight divided by height squared: 77 divided by 1.753 squared. 1.753 squared is 3.073, and 77 divided by 3.073 is 25.1.
Interpretation: 25.1 sits a hair over the overweight line of 25, while his weight is only 6.3 kilograms above the Devine estimate — both readings of the same body. For a muscular man this is the classic BMI misfire; the numbers disagree because they see different things, and neither sees composition. That is why clinicians read both numbers together and still ask more questions.
CHAPTER 07Example 6: Adjusted Body Weight — 5 Feet 10 Inches, 110 Kilograms
From Example 1, IBW is 73.0 kilograms. Actual weight is 110 kilograms, so the gap is 110 minus 73 — that is 37 kilograms.
Adjustment: 0.4 times 37 is 14.8. Adjusted body weight equals 73 plus 14.8, so 87.8 kilograms, about 193.6 pounds.
Interpretation: the dosing weight sits deliberately between actual and ideal, because excess tissue is part fat and many drugs ignore fat. You now understand an arithmetic step performed quietly on hospital wards every day — and also why you should never perform it for yourself: which factor applies, and whether it applies, is a clinical decision tied to the specific drug.
CHAPTER 08Cross-Checks and Cautions
Verify any calculator with three habits. Recompute one example by hand and confirm the tool agrees to within rounding. Check the sex constant: 50 versus 45.5 kilograms is the fingerprint of which base the tool used. And convert with 2.205, not 2.0 or 2.2 — sloppy conversion factors are the most common source of pound-level disagreement between tools. Run your own height through /ideal-body-weight-calculator.html and confirm it against your hand math.
Then hold the standing caution. Six examples, one formula, zero knowledge of any real body: these are educational estimates of a 1974 dosing convention. Use them to understand what the number on a chart means and where it came from — not to set a target, judge a body, or make a health decision. For those, the formula is one input among many, and clinicians own the weighting.
One last cross-check worth keeping: the female base of 45.5 kilograms against the male 50 means any two people of the same height differ by exactly 4.5 kilograms in their Devine estimates. If a tool's male and female outputs differ by something else, it is mixing formulas mid-page — a small flaw that says a lot about how carefully the rest was built.
🔑 Key takeaways
- Devine in one line: 50 kg plus 2.3 kg per inch over five feet for men; 45.5 plus 2.3 for women; 1 kg equals about 2.205 pounds.
- Example 1 shows the whole machine: 5'10" male becomes 50 plus 23 — that is 73 kg, about 161 lb.
- Below five feet the formula subtracts 2.3 kg per inch (Example 4: 4'11" gives 43.2 kg) — but this is extrapolation, so treat it with caution.
- Example 5's cross-check is the real lesson: Devine says 70.7 kg, BMI says 25.1 — different questions, honest disagreement, neither sees muscle.
- Adjusted body weight is IBW plus 0.4 times the actual-minus-ideal gap: 73 plus 0.4 times 37 gives 87.8 kg.
- Check any calculator's sex constant and conversion factor, and treat every output as a dosing-era estimate — not a target and not medical advice.
❓ Frequently asked questions
Why does the formula add weight per inch rather than using BMI directly?
Because it predates routine BMI use and was built for dosing arithmetic that clinicians could do in their heads. The linear-per-inch design is easy and consistent, which mattered more in 1974 — and still does at the bedside.
My IBW seems low compared with what I weigh at a healthy BMI. Is that a problem?
Usually no. The Devine estimate is deliberately lean and sits near a BMI of roughly 22 to 23 for many heights, while the normal band extends well above that. A healthy weight range is a range; the dosing reference is one point inside it.
Which IBW do hospitals actually use?
Conventions vary by institution and by drug, but Devine is the most common default in the United States, with some protocols specifying ideal, others adjusted, and others actual weight. The choice is clinical policy, not preference.
Is 2.3 kilograms per inch the same for men and women?
Yes — the slopes match; only the five-foot base differs (50 versus 45.5 kilograms). That is why the male-female gap in estimates is a constant 4.5 kilograms at any height above five feet.
Can I use these examples for pregnancy or for athletes?
Neither, without clinical guidance. Pregnancy changes fluid and weight baselines entirely, and athletes' muscle mass breaks the equation's average-composition assumption — adjusted body weight and dosing decisions there are clinician territory.
Does rounding change the results much?
Display rounding moves the answer by at most a few tenths of a kilogram — a pound at most in pounds. If a tool disagrees with your hand math by more than that, check its conversion factor or its inches-over-five-feet input first.
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