"What's my ideal weight?" is one of the most-searched fitness questions — and the most misleading. There is no single "ideal." There is a range that history, biology and statistics agree is broadly healthy for your height. This guide walks through the three classic formulas, what they actually estimate, and how to read the answer without falling into the trap of chasing one perfect number.
Quick Answer
For adults, the three formulas you'll see most are:
- Devine (1974) — Men: 50 kg + 2.3 × (in over 60); Women: 45.5 kg + 2.3 × (in over 60)
- Robinson (1983) — Men: 52 + 1.9 × (in over 60); Women: 49 + 1.7 × (in over 60)
- Miller (1983) — Men: 56.2 + 1.41 × (in over 60); Women: 53.1 + 1.36 × (in over 60)
All three were originally derived for medical dosing, not athletic performance. Treat the spread between them as a healthy weight range, not a target. Compute yours in seconds with our Ideal Weight Calculator.
Where the Formulas Came From
Devine's equation was published in 1974 to dose certain medications (notably aminoglycosides) based on lean body mass rather than total weight. Robinson and Miller refined the same idea in the early 1980s. They were never designed as nutrition or training tools — they are clinical estimators of typical lean mass at a given height.
That historical purpose explains their structure:
- A base weight at 5 ft (60 in)
- A constant kg added for every inch above that base
- Different constants for men and women
It also explains their limits: someone with above-average muscle, dense bones, or simply a larger frame will sit above any of these numbers without being unhealthy.
How to Read the Spread
Plug a 180 cm (≈ 70.9 in) man in to all three:
- Devine: 50 + 2.3 × 10.9 ≈ 75 kg
- Robinson: 52 + 1.9 × 10.9 ≈ 72.7 kg
- Miller: 56.2 + 1.41 × 10.9 ≈ 71.6 kg
That ~3 kg spread is your honest answer. Aiming inside the range — say 72–75 kg — is reasonable; aiming for exactly 73.4 kg is precision the formulas were never designed to give.
For a 165 cm (≈ 65.0 in) woman:
- Devine: 45.5 + 2.3 × 5 ≈ 57 kg
- Robinson: 49 + 1.7 × 5 ≈ 57.5 kg
- Miller: 53.1 + 1.36 × 5 ≈ 59.9 kg
Range ~57–60 kg. Pair this with the WHO healthy BMI band (18.5–24.9) and you get a wider, evidence-based corridor.
"Ideal" Weight vs. BMI Healthy Range
BMI gives the broadest validated range; ideal-weight formulas give a tighter "typical lean adult" estimate within it.
For the 180 cm man, healthy-weight by BMI is:
- 18.5 × 1.80² ≈ 59.9 kg → 24.9 × 1.80² ≈ 80.7 kg
So 60–80 kg by BMI, with the three "ideal" formulas clustering around 72–75 kg. Most lean, recreationally active adults sit in the upper third of the BMI range; serious lifters often sit above the formulas without being unhealthy. Use our BMI Calculator as the wider sanity check.
Where the Formulas Are Useful
- A first benchmark when you have no other data and want a rough target
- Medical dosing (their original use) when a body-weight-normalised drug needs lean mass
- Pre-cut targets for people with no athletic background who want a generic landing point
In any of these cases, treat the formula answer as a starting line for a conversation, not a verdict.
Where They Fall Short
- Muscular adults. Anyone with significant resistance-training history can comfortably sit 5–10 kg above any of these formulas at low body fat.
- Older adults. Sarcopenia drives lean mass down; the "ideal weight" can become a hollow shell of mostly fat. Pair with body fat percentage.
- Pediatric and adolescent use. Children use age- and sex-specific percentile charts, not these adult formulas.
- Very short or very tall adults. The linear "inches above 5 ft" relationship gets less accurate at the extremes.
- Body composition. Two people at the same ideal-weight estimate can have very different fat-to-lean ratios.
When the formula answer feels off — your number says 70 kg but you train hard and look healthy at 78 — trust measurements (waist circumference, body fat percentage, blood markers) over the formula.
Combining Ideal Weight With Other Metrics
A practical, low-noise picture of healthy body weight uses three numbers together:
- BMI — broad health range (our BMI Calculator)
- Body fat % — composition layer (our Body Fat Calculator)
- Ideal-weight formula spread — a tighter, traditional reference range
If all three agree you are in healthy territory, you almost certainly are. If they disagree, the disagreement itself is the useful signal — usually because muscle mass is high (formulas under-shoot) or sedentary fat mass is high (formulas + BMI in normal range but body fat % flags it).
Sample Use Cases
Returning to fitness after years off
A 50-year-old, 175 cm man who used to lift and weighs 95 kg today. Devine/Robinson/Miller cluster around 73 kg. BMI says 60–76 kg healthy. He is not aiming to be 73 kg in 8 weeks. He is using 70–80 kg as a sensible 12-month corridor and using body fat % to make sure the loss is fat, not muscle.
Cutting for the first time
A 25-year-old, 165 cm woman at 70 kg, BMI 25.7. Formulas suggest 57–60 kg, BMI healthy range is 50–68 kg. Picking 62–65 kg as a first goal — well inside the healthy band, above the strict formula answer — is a reasonable, sustainable target that respects she's not a clinical patient.
Other Ideal-Weight Formulas Worth Knowing
Beyond Devine, Robinson and Miller, a few additional formulas appear in clinical and research settings:
Hamwi (1964)
The oldest still-cited formula:
- Men: 48 kg + 2.7 × (in over 60)
- Women: 45.5 kg + 2.2 × (in over 60)
Used in nutritional support calculations; tends to land near Devine for men, lower for women.
Broca Index
A simplification dating to the 19th century:
Ideal weight (kg) ≈ height (cm) − 100 (men) Ideal weight (kg) ≈ height (cm) − 105 (women)
Imprecise but quick. Often used as a rough mental check.
Lemmens (BMI-anchored)
A modern reframing: pick the BMI of 22 as a population midpoint, then back out:
Ideal weight = 22 × height² (m²)
A 180 cm adult → 22 × 3.24 ≈ 71 kg. Surprisingly close to Devine for most heights.
All these formulas exist because none of them is "right." They are different ways to triangulate the same conceptual range.
Ideal Weight vs. Goal Weight
A common confusion: ideal weight (population estimate) is not the same as goal weight (your personal target).
- Ideal weight answers: "What does the average healthy adult my height weigh?"
- Goal weight answers: "What weight do I want to live at, given my lifestyle, training and preferences?"
For an athlete, goal weight often sits 5–10 kg above ideal. For someone returning from a long gain, goal weight sits inside the formula range but a few kg above the smallest answer.
Pick a goal weight you can defend with three reasons (e.g., "I look how I want, I lift comfortably, my blood markers are good"). The formula is only one of those reasons.
Frame Size as a Modifier
Ideal-weight formulas assume medium frame. Frame size can shift the realistic target by ±10%.
A simple frame estimate uses wrist circumference relative to height:
| Wrist / height ratio | Frame size | |---|---| | < ~10.4 | Small | | 10.4–10.9 | Medium | | > 10.9 | Large |
Most adults are within the medium band; outliers should adjust their ideal-weight expectations accordingly. Frame size is structural, not changeable — accept it as a parameter.
Common Misuses
- Treating the smallest formula answer as the "right" weight. It isn't. Stay inside the spread.
- Using ideal weight to "calculate" a calorie target. Calorie needs come from your current weight, height, age and activity. See our Calorie Calculator.
- Comparing yourself to a formula meant for medication dosing. Use it as a sanity check, not a verdict.
- Ignoring waist circumference. Two adults at the same "ideal weight" with very different waist sizes carry very different health risk.
Frequently Asked Questions
Why are there three different formulas?
Each was published independently to address slightly different patient populations and analytical methods in the 1970s–80s. They mostly agree; the disagreement is honest — there's no single right answer.
What "ideal weight" should I aim for if the formulas disagree?
Use the range. If Devine says 75, Robinson says 73, and Miller says 72, then 72–75 kg is the answer. Pick a target inside the range, not a specific decimal.
Are these formulas different for athletes?
They under-estimate ideal weight for trained athletes with significant muscle. Combine with body fat percentage; if you are at a healthy body fat % above the formula's number, the formula is the one that's wrong for you — not your body.
Do the formulas work in metric and imperial?
The underlying inputs are inches above 5 ft and a kilogram output. Our Ideal Weight Calculator handles both metric and imperial automatically.
Should I use these instead of BMI?
Use both. BMI gives you the broad healthy range; the ideal-weight formulas tighten it into a typical-lean target. They work better together than either does alone.
Bottom Line
There is no single "ideal weight" — but there is a defensible healthy range, and three classical formulas help define it.
- Compute the spread with our Ideal Weight Calculator.
- Cross-check with the BMI healthy range using our BMI Calculator.
- Layer in body fat % for composition.
- Pick a target inside the resulting corridor, not at a single decimal.
A range you can hit and hold beats a perfect number you can't.
Health and fitness calculations are estimates only and not medical advice. If you have a medical condition, are very lean, very heavy, pregnant, or significantly outside these ranges, consult a healthcare provider or registered dietitian for a personalised assessment.