# Ideal Body Weight Calculator: Devine, Robinson, Miller and Hamwi Formulas Side by Side

Page: https://hirantha.me/tools/ideal-weight-calculator
Part of: Hirantha Sandaruwan Lakshan free tools (https://hirantha.me/tools)
Updated: 2026-10-13

See ideal body weight for your height by the Devine, Robinson, Miller and Hamwi formulas side by side, with the BMI-based healthy range for comparison.

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Enter your sex and height to see the ideal body weight given by four classic formulas, Devine (1974), Robinson (1983), Miller (1983) and Hamwi (1964), side by side in kilograms and pounds, with the BMI-based healthy range for comparison. The formulas were written to estimate drug doses or as rules of thumb, not as health targets, and the page says where each came from. It is for adults: children and teenagers are still growing and are judged on growth charts. This is general information, not medical advice. Nothing you type leaves your device.

Each formula is a straight line: a base weight at 5 feet plus a fixed amount for every inch above 5 feet (60 inches). Devine: men 50 kg + 2.3 kg per inch, women 45.5 kg + 2.3 kg per inch, which is printed exactly this way as the predicted body weight in the NIH NHLBI ARDS Clinical Network ventilator protocol. Robinson: men 51.65 kg + 1.85 kg per inch and women 48.67 kg + 1.65 kg per inch, as in the abstract of the 1983 paper (many calculators round these to 52 + 1.9 and 49 + 1.7). Miller: men 56.2 kg + 1.41 kg per inch and women 53.1 kg + 1.36 kg per inch, the constants most widely published and the ones in the PENG statement on ideal body weight. We could not open the original 1983 letter, and a 2021 commentary prints 55.7 + 1.39 and 53 + 1.33, which is within 1 kg of these for heights up to 7 feet. Hamwi is in pounds: men 106 lb + 6 lb per inch and women 100 lb + 5 lb per inch.

They were not designed as health targets. Devine's equations came from the use of ideal body weight to estimate drug dosing, and they matched an older rule of thumb built on insurance height and weight tables. Robinson and Miller derived their equations by regression on Metropolitan Life Insurance height and weight tables, for drug dosage calculations. For Hamwi no method of development has been reported. A 2000 history of the equations (Pai and Paloucek) found they are alike because the height-weight tables they came from broadly agree, and that over the years the ideal weight from such tables was read as a fat-free weight and used as a stand-in for lean body weight.

The formulas start at 5 feet (152.4 cm). Below that they would have to be stretched past the heights they were built for, so for shorter adults the tool shows only the BMI-based range. Results are rounded half up to 0.1 kg and 0.1 lb. Pounds come from kilograms with the exact factor 0.45359237.

The BMI-based range for your height is the weight that gives a BMI of 18.5 up to 24.9 (the WHO normal range) or up to 22.9 (the Asian cut-offs in the Sri Lanka Ministry of Health Nutrition Division table and the WHO Western Pacific 2000 report). The Ministry's 2018 obesity guideline also prints an acceptable weight range for a BMI of 18.5 up to 23, for example 43 to 53 kg at 5 ft 0 in and 52 to 65 kg at 5 ft 6 in.

The four formulas: constants by sex, for height above 5 feet (60 inches):
| Formula | Year | Men | Women | Basis |
| --- | --- | --- | --- | --- |
| Devine | 1974 | 50 kg + 2.3 kg per inch | 45.5 kg + 2.3 kg per inch | Used to estimate drug doses; printed in the NIH NHLBI ARDS Network protocol |
| Robinson | 1983 | 51.65 kg + 1.85 kg per inch | 48.67 kg + 1.65 kg per inch | Regression on Metropolitan Life tables, for drug dosage calculations |
| Miller | 1983 | 56.2 kg + 1.41 kg per inch | 53.1 kg + 1.36 kg per inch | Later Metropolitan Life tables, for drug dosage calculations |
| Hamwi | 1964 | 106 lb + 6 lb per inch | 100 lb + 5 lb per inch | Rule of thumb; no method of development reported |

Q: What is my ideal weight?
A: There is no single ideal weight. These formulas give estimates from height and sex only, and they were written for drug dosing or as rules of thumb, not as health targets. The BMI-based range shown beside them is a screening range. A doctor or other qualified health professional can tell you what is healthy for you, taking age, muscle, health and history into account.

Q: Which ideal weight formula is the most accurate?
A: None has been shown to be an accurate health target, because ideal weight is not something that can be measured. The 2000 history of the equations by Pai and Paloucek concluded that they are similar because the height-weight tables behind them broadly agree, so any one of them may be used to estimate ideal body weight. That is a statement about similarity, not about health.

Q: Why do the formulas give different numbers?
A: They use different base weights and different amounts per inch, and they come from different tables and decades. They also differ from other calculators that round the constants. Robinson's published constants are 51.65 kg + 1.85 kg per inch for men, but many sites round them to 52 + 1.9, which adds up to a kilogram at 6 feet. A 2021 commentary lists slightly different Miller constants from the widely published ones.

Q: Were these formulas made for drug dosing?
A: Devine, Robinson and Miller were: ideal body weight was used to estimate drug doses and clearance, and Robinson's 1983 paper is titled Determination of ideal body weight for drug dosage calculations. Hamwi's is a rule of thumb for which no method of development has been reported. None of them was developed as a target for healthy weight.

Q: Why does the calculator not show the formulas below 5 feet?
A: Because they are straight lines that start at a base weight at 5 feet. Below 5 feet you would have to apply them past the heights they were built for, and the results would not mean much. For adults under 5 feet (152.4 cm) the tool shows the BMI-based weight range only.

Q: Do these formulas suit Sri Lankans and other Asian populations?
A: They come from, or match, insurance height and weight tables rather than Asian populations, and they use height and sex only. The WHO expert consultation of 2004 found that risk in Asian populations can start at a lower BMI than in European populations, so the BMI-based range here is shown on both the WHO cut-offs (18.5 to 24.9) and the Asian cut-offs (18.5 to 22.9) used by the Sri Lanka Ministry of Health and the WHO Western Pacific Region.

Q: Should I try to reach my ideal weight?
A: That is a personal health decision, and this page cannot make it for you. A formula result is not a goal. If you are thinking about changing your weight, talk to a doctor or another qualified health professional first, who can look at your whole health and not just your height.

Q: How do I convert kilograms to pounds?
A: Divide kilograms by 0.45359237 to get pounds, or multiply by about 2.2046. The tool shows both for you. For other conversions, use the weight converter and the length converter linked below.

Sources: Pai MP and Paloucek FP, The origin of the ideal body weight equations, Ann Pharmacother 2000 (abstract), checked 2026-10-13 (https://pubmed.ncbi.nlm.nih.gov/10981254/); NIH NHLBI ARDS Clinical Network, Mechanical Ventilation Protocol Summary (predicted body weight: males 50 + 2.3 x [height in inches - 60], females 45.5 + 2.3 x [height in inches - 60]), checked 2026-10-13 (https://www.ardsnet.org/files/ventilator_protocol_2008-07.pdf); Robinson JD et al., Determination of ideal body weight for drug dosage calculations, Am J Hosp Pharm 1983 (abstract with the equations), checked 2026-10-13 (https://pubmed.ncbi.nlm.nih.gov/6869387/); Miller DR et al., Determining ideal body weight (and mass), Am J Hosp Pharm 1983 (PubMed record of the letter, no abstract), checked 2026-10-13 (https://pubmed.ncbi.nlm.nih.gov/6638023/); Chichester S, Holmes TM and Hubbard J, Ideal body weight: a commentary, Clin Nutr ESPEN 2021 (Table 1 of IBW formulas including Hamwi 1964 in pounds), checked 2026-10-13 (https://pmc.ncbi.nlm.nih.gov/articles/PMC8646317/); Pinnock G, Statement on Ideal Body Weight, PENG pocket guide (Table 1 lists the Hamwi, Devine, Robinson and Miller formulas, including Miller 56.2 + 1.41 and 53.1 + 1.36), checked 2026-10-13 (https://www.peng.org.uk/pdfs/pocket-guide/statement-on-ideal-body-weight.pdf); Ministry of Health Sri Lanka, Guideline on Management of Overweight and Obesity among Adults in Sri Lanka, 2018 (Annex 5, acceptable weight range for BMI 18.5 to 23), checked 2026-10-13 (https://www.ncd.health.gov.lk/images/pdf/Guildlines/Guideline_Obesity.pdf); WHO Western Pacific Region, The Asia-Pacific perspective: redefining obesity and its treatment, 2000, checked 2026-10-13 (https://iris.who.int/items/a74d8440-5c1d-4237-9559-3f729058587b)

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