Ideal Body Weight Calculator

Methodology

Devine, Robinson, Miller and Hamwi equations

IBW = base + k × (height in inches − 60); Devine: men 50 + 2.3k, women 45.5 + 2.3k

Each equation starts from a base weight at 5 feet (152.4 cm) and adds a fixed amount per inch above that. Devine's is a commonly used equation, including in drug-dosing contexts. Robinson uses its original 1983 coefficients; Hamwi, published in pounds, is converted exactly.

Who it is for

Adults with a height of 152 cm (60 in) or more.

Version

2.1.0

How this calculator works

Where the formula comes from

• The Devine equation appeared in 1974 in a paper on gentamicin dosing; it was not derived or validated against measured healthy weight or health outcomes.^[1]
• A 2000 review traced the ideal body weight equations to historical insurance-company height–weight tables.^[1]
• Robinson and colleagues (1983) derived their equations by regression of median weight on height from the Metropolitan Life Insurance tables.^[2]
• The Miller equations were published in 1983 as a short communication in the American Journal of Hospital Pharmacy.^[3]
• Hamwi's 1964 method was given in pounds: 106 lb plus 6 lb per inch above 5 feet for men, and 100 lb plus 5 lb per inch for women.^[1][4]

The inputs

• Each equation uses only sex and height: a base weight at 5 feet (60 inches, 152.4 cm) plus a fixed amount for every inch above 5 feet.^[1]
• In the Devine equation the base weight is 50 kg for men and 45.5 kg for women, with 2.3 kg added per inch above 5 feet.^[1]

Versions and alternatives

• The Miller equations are commonly reproduced as 56.2 kg + 1.41 kg/in (men) and 53.1 kg + 1.36 kg/in (women); the Robinson equations are often reproduced in a rounded form, 52 kg + 1.9 kg/in (men) and 49 kg + 1.7 kg/in (women).^[2][3]
• Robinson's original paper reports more precise coefficients, 51.65 kg + 1.85 kg/in for men and 48.67 kg + 1.65 kg/in for women; the rounded form is the one usually reproduced.^[2]
• The ARDS Network trial calculated predicted body weight as 50 (men) or 45.5 (women) + 0.91 × (height in cm − 152.4), which gives the same values as the Devine equation.^[5]
• A 2016 equation estimates the weight corresponding to any chosen body mass index from height, instead of a single fixed reference weight.^[4]
• Lean body weight, estimated for example by the 2005 Janmahasatian equation from height, weight and sex, is a different body-size measure that was derived from measured body-composition data.^[6]

Where accuracy falls (published evidence)

• The equations give different results for the same person, and they do not correspond to a consistent body mass index across different heights.^[7][1]
• Height and sex alone do not account for body composition, frame size or medical conditions.^[7]
• The equations are defined only for heights of 5 feet (152.4 cm) and above.^[1]
• For drug dosing, the appropriate weight descriptor (total, ideal or adjusted body weight) depends on the medicine; no single equation suits every drug or every body size.^[8]

What guidelines say

• The ARDS Network trial set tidal volume at 6 mL per kg of predicted body weight in acute lung injury and ARDS.^[5]
• The Surviving Sepsis Campaign 2021 guidelines recommend a low tidal volume, about 6 mL/kg of predicted body weight, in adults with sepsis-induced ARDS.^[9]

Sources

1. Pai MP, Paloucek FP. The origin of the "ideal" body weight equations. Ann Pharmacother. 2000;34(9):1066–1069. doi:10.1345/aph.19381
2. Robinson JD, Lupkiewicz SM, Palenik L, Lopez LM, Ariet M. Determination of ideal body weight for drug dosage calculations. Am J Hosp Pharm. 1983;40(6):1016–1019. doi:10.1093/ajhp/40.6.1016
3. Miller DR, Carlson JD, Lloyd BJ, Day BJ. Determining ideal body weight (and mass). Am J Hosp Pharm. 1983;40(10):1622–1625. doi:10.1093/ajhp/40.10.1622a
4. Peterson CM, Thomas DM, Blackburn GL, Heymsfield SB. Universal equation for estimating ideal body weight and body weight at any BMI. Am J Clin Nutr. 2016;103(5):1197–1203. doi:10.3945/ajcn.115.121178
5. The Acute Respiratory Distress Syndrome Network. Ventilation with lower tidal volumes as compared with traditional tidal volumes for acute lung injury and the acute respiratory distress syndrome. N Engl J Med. 2000;342(18):1301–1308. doi:10.1056/NEJM200005043421801
6. Janmahasatian S, Duffull SB, Ash S, Ward LC, Byrne NM, Green B. Quantification of lean bodyweight. Clin Pharmacokinet. 2005;44(10):1051–1065. doi:10.2165/00003088-200544100-00004
7. Ideal body weight: a commentary. Clin Nutr ESPEN. 2021;46:246–250. doi:10.1016/j.clnesp.2021.09.746
8. Pai MP. Drug dosing based on weight and body surface area: mathematical assumptions and limitations in obese adults. Pharmacotherapy. 2012;32(9):856–868. doi:10.1002/j.1875-9114.2012.01108.x
9. Evans L, Rhodes A, Alhazzani W, et al. Surviving Sepsis Campaign: international guidelines for management of sepsis and septic shock 2021. Crit Care Med. 2021;49(11):e1063–e1143. doi:10.1097/CCM.0000000000005337

Compiled from the published sources above. Every statement was agreed independently by three AI research tools (Claude, ChatGPT, DeepSeek) and its source verified in PubMed or Crossref by the Hakeemly editorial team. Not reviewed by a doctor unless stated. Agreed on 2026-10-11

Worked example: how to calculate ideal body weight

Calculation:

170 cm = 66.93 in: 50 + 2.3 × 6.93 = 65.94

An illustration with sample values, worked out with the same method the tool above uses.

Limitations

• These equations estimate a reference weight; they are not a weight-loss target.
• They ignore age, body frame and muscle mass.
• Not for children.

References

1. Devine BJ. Gentamicin therapy. Drug Intell Clin Pharm. 1974;8:650–655.
2. Pai MP, Paloucek FP. The origin of the "ideal" body weight equations. Ann Pharmacother. 2000;34(9):1066–1069. doi:10.1345/aph.19381