Healthy Weight vs Ideal Weight: WHO Band vs Devine and Friends

DevOkk keeps them on separate pages so the labels stay honest. Healthy Weight Calculator is the WHO screening interval from height only. Ideal Weight Calculator is Devine, Robinson, Miller, and Hamwi. BMI Calculator is the index those bands sit on. None of this is a personal goal assigned by a website. None of it is a diagnosis. Height is not uploaded to finish the math.

The BMI caveats - athletes, children, pregnancy, eating disorders - are Why BMI is not a diagnosis. Composition is Navy body fat vs DEXA.

Healthy weight here is algebra on the WHO table

Adult BMI = kg / m². Rearrange: kg = BMI × m². For a “normal” adult band of 18.5–24.9, you get a minimum mass and a maximum mass at one height.

Default 175 cm = 1.75 m. m² = 3.0625.

• 18.5 × 3.0625 ≈ 56.66 kg
• 24.9 × 3.0625 ≈ 76.26 kg

That interval is what the healthy-weight tool prints (with pounds beside it). It does not pick 22 because 22 is fashionable. It does not ask sex, because the common WHO adult cutoffs used here are not sex-split. A 20 kg spread at average height is the feature. Anyone selling a single “healthy” kilogram at 175 cm without a clinical context is compressing a band into a slogan.

Overweight and underweight sibling pages are the same table with a different headline: Overweight Calculator, Underweight BMI Calculator.

IBW formulas are named point estimates from height and sex

Ideal body weight equations showed up in clinical teaching as a way to scale some drug doses and to talk about “expected” mass from height when actual mass was extreme. They were not fitness goals. They were not BMI. They disagree.

Devine (a common teaching form):

• Male: 50 kg + 2.3 kg × (inches over 5 feet)
• Female: 45.5 kg + 2.3 kg × (inches over 5 feet)

Male, 5 ft 10 in: 10 inches over 5 feet → 50 + 23 = 73.0 kg. That is the sample on DevOkk. Robinson, Miller, and Hamwi use different intercepts and inches coefficients. The tool shows all four so you can see the spread. If they matched, we would only ship one.

Hamwi in particular is often remembered as a “rule of thumb” from mid-20th-century tables. Using it as a 2026 lifestyle target is a category error. Using any of them to dose a medication from a public webpage is a worse category error. Pharmacokinetics, renal function, and the actual drug monograph are not in the form.

Worked comparison at one height

Take the male 5 ft 10 in (178 cm) Devine result of 73 kg.

BMI at 178 cm: 73 / (1.78)² ≈ 73 / 3.1684 ≈ 23.0. That happens to sit inside 18.5–24.9. That is coincidence of this example, not proof that Devine is the healthy-weight band.

The healthy-weight interval at 178 cm:

• 18.5 × 3.1684 ≈ 58.6 kg
• 24.9 × 3.1684 ≈ 78.9 kg

Devine 73 kg is one point inside a 20 kg window. Robinson or Hamwi will sit somewhere else in or even near the edge of that window. A female Devine at the same height is lower than male Devine; the WHO band at that height did not change. Sex entered IBW because the old equations were fit that way, not because the WHO interval became sex-specific on DevOkk.

If you only ever saw IBW, you would think health is a needle. If you only ever saw the WHO band, you would think health is a 20 kg hallway. Both are simplifications. The hallway is at least honest about width.

Female Devine at the same height is a different point

Female Devine at 5 ft 10 in: 45.5 + 2.3×10 = 68.5 kg. The WHO band at 178 cm did not move; it is still about 58.6–78.9 kg. Both 68.5 and 73.0 can sit inside that hallway. IBW told you sex mattered. The healthy-weight tool told you it did not, because it is BMI algebra on a unisex adult table.

Hamwi (a common restatement) is 48.0 kg + 2.7 kg per inch over 5 feet for men, and 45.5 kg + 2.2 kg per inch for women. At male 5 ft 10 in that is 48 + 27 = 75.0 kg, two kilograms above Devine. Miller and Robinson sit in the same neighborhood with different intercepts. The comparison table on the tool exists so you stop treating “ideal” as a trademarked kilogram.

Magazines that print “BMI 22” as the goal are picking a point inside 18.5–24.9 because it looks decisive. 22 × 3.1684 ≈ 69.7 kg at 178 cm - yet another point, not Devine, not Hamwi. DevOkk’s healthy-weight page refuses to collapse the band. That is the honest UX.

Some adult clinical notes for people of Asian ancestry use overweight cutoffs near BMI 23 rather than 25. If your clinician uses that table, the 24.9 upper edge on DevOkk is the WHO teaching band, not a veto of your clinic. Do not hunt the internet for the cutoff that blesses today’s scale reading.

Adjusted body weight is yet another formula

Some dosing notes use adjusted body weight when actual weight is far above IBW (a blend of IBW and actual). DevOkk’s ideal-weight page is not that calculator. If a hospital protocol names adjusted body weight, use the protocol and the pharmacy, not a comparison table on a tools site.

Actual body weight, IBW, and adjusted body weight can all appear in the same clinical sentence. A consumer “ideal weight” search result usually means Devine-or-similar. Read the label on the page you opened.

Hamwi, Robinson, and Miller are not rounding error

Robinson (male) is often taught as 52 kg + 1.9 kg per inch over 5 feet. At 10 extra inches that is 52 + 19 = 71.0 kg, below Devine’s 73. Miller is often 56.2 + 1.41×inches over 5 feet for men → 56.2 + 14.1 = 70.3 kg. Same height, four names, a several-kilogram spread before you even argue about shoes.

If a forum says “your IBW is 73,” they silently picked Devine. If a nurse said 70, they may have picked Miller. DevOkk shows the set so the argument is visible. None of the four is “the healthy-weight calculator in disguise.” The healthy-weight interval at 5 ft 10 in is still tens of kilograms wide.

Clothing size charts that map a chest measurement to a kilogram are merchandising. They do not belong in the same sentence as WHO BMI 18.5.

Same mass, two headlines

Type 73 kg and 178 cm into BMI Calculator and you get about 23.0, “normal.” Type only 178 cm into Healthy Weight Calculator and 73 kg is one occupant of a hallway. Type the same height into Ideal Weight Calculator and Devine may print 73 as if it were the destination. The scale did not change. The headline did.

That is why this is a comparison post, not a “which is more accurate” post. Accuracy would require a clinical question: dosing scalar, population screening band, or body composition. IBW is the first, WHO interval is the second, Navy tape is neither.

Frames, clothing size, and the missing variables

Neither tool asks frame size, ethnicity-specific BMI cutoffs, waist, or training. “Small frame / large frame” adjustments exist in some old IBW variants. DevOkk’s comparison is the four named core equations, not every pamphlet from 1982.

A clothing size is not IBW. BMI 22 as a fashion target is not the healthy-weight calculator. If a coach set a competition weight, that is sport, not WHO.

Pregnancy, children, and amputation

The healthy-weight band is adult, non-pregnant BMI algebra. Pediatric percentiles are different. Pregnancy is not this interval. Limb loss changes how you interpret mass versus height; neither page is built as a prosthesis clinic tool.

Due date from LMP is Due Date Calculator - a calendar, not a weight goal.

Privacy and shared screens

Both calculators run locally. Height and sex (where used) stay in the tab. localStorage can persist the last run. Clear it. A screenshot of “ideal 73 kg” is not a prescription.

Do not enter a partner’s height to produce a scolding number. The ethics problem is the same as weaponizing BMI.

Two formulas, one bathroom scale

Open Healthy Weight Calculator when you want the WHO adult interval at a height. Open Ideal Weight Calculator when you need to see why Devine, Robinson, Miller, and Hamwi refuse to agree. Open BMI Calculator when you already have a mass and want the index. Then treat all of it as labeled arithmetic. The scale in the bathroom still only knows kilograms. It does not know which paper you wanted it to match.