Ideal Weight Calculator — Devine Formula (Kg + Lbs)

This ideal weight calculator estimates a reference body weight for an adult based on height and biological sex using the Devine formula. An ideal weight calculator like the one on this page turns two easy inputs into a clinical-grade reference number in under a second, which is why the ideal weight calculator format has become the default explainer used by health portals when they need to translate a height reading into a familiar kilogram target. The Devine formula behind this ideal weight calculator was first published in 1974 by clinical pharmacist B. J. Devine for calculating aminoglycoside antibiotic doses. The Devine equation is now the reference default across major clinical drug-dosing guidelines and remains the most widely implemented ideal body weight formula in electronic hospital prescribing systems worldwide. The formulation is elegantly compact: for men the reference is 50 kg plus 2.3 kg for every inch of height above five feet; for women the reference is 45.5 kg plus 2.3 kg per inch above five feet. Height is entered here in centimetres and converted internally (one inch equals 2.54 cm) so users on either unit system get an identical answer. The origin of the equation, its arithmetic derivation, and its clinical uses were reviewed in detail by Pai and Paloucek in Annals of Pharmacotherapy in 2000, and it continues to be endorsed by NIH pharmacokinetic guideline material and by BMJ therapeutics reviews from 2015 onwards. Because the Devine value depends on only two inputs, it is fast to compute at the bedside and reproducible without specialised software, which is the reason it survives in NHS, CDC, and WHO reference tables even where more recent formulas exist. In everyday use, the value returned here is a starting anchor rather than a target: it tells you where a person of that height and sex sits in the reference distribution used by clinicians when they need one number quickly, for example when scaling drug doses in intensive care, when calibrating tidal volume in lung-protective ventilation, or when triaging bariatric referrals. For the general public the same number provides a plain-language reference point that pairs well with a BMI reading and a body-fat estimate: BMI captures relative mass, body-fat captures composition, and the Devine ideal weight captures the specific numerical target that clinical literature has used for half a century. Together those three numbers turn a single height measurement into a small evidence-based dossier that a person can carry into a GP appointment, a nutritionist consultation, or a self-directed training plan without needing further calculation. The output shown on the results panel is rounded to two decimal places for readability and the same calculation runs identically on desktop, on mobile, and when the calculator is embedded on partner sites, so a person can revisit the tool from a different device and expect the same reference weight for the same height and sex input every time.

Let's calculate the ideal weight for a 170 cm tall woman. First, convert height to inches: 170 cm ÷ 2.54 = 66.93 inches. Then apply the Devine formula for women: IBW = 45.5 + 2.3 × (66.93 - 60) = 45.5 + 2.3 × 6.93 = 45.5 + 15.94 = 61.44 kg. So, the ideal weight for a 170 cm woman is 61.44 kg. This means that for optimal health, a woman of this height might aim for a weight around 61 kg. However, individual factors like muscle mass and body composition should also be considered. For a man of the same height, the calculation would be: IBW = 50 + 2.3 × (66.93 - 60) = 50 + 2.3 × 6.93 = 50 + 15.94 = 65.94 kg. Thus, the ideal weight for a 170 cm man is 65.94 kg. These examples illustrate how the formula adjusts based on gender, providing a personalized estimate for each individual.

The ideal weight calculator on this page matters because maintaining a body weight within a well-defined reference range is one of the strongest modifiable predictors of long-term cardiometabolic and musculoskeletal health across the adult life course. Large-scale prospective analyses published in the New England Journal of Medicine (2017) and pooled cohort data from the Global BMI Mortality Collaboration in The Lancet (2016, over 10.6 million participants) both show a U-shaped relationship between weight and all-cause mortality, with the lowest risk concentrated near the reference range that formulas such as Devine target. A large JAMA Internal Medicine analysis (2018) linked sustained weight variability outside that reference band to elevated risk of type-2 diabetes and cardiovascular events, independent of average BMI. Guidance from NICE (guideline CG189, updated 2022) and WHO adult obesity technical reports (2020) uses a comparable reference weight approach when estimating dosing, dietary energy needs, and rehabilitation targets. On the lower end of the spectrum, being persistently underweight is associated in Cochrane systematic reviews (2019 and 2021) with reduced immune competence, sarcopenia, delayed wound healing, and higher post-operative complication rates; those risks rise sharply in older adults and in people recovering from cancer treatment. On the upper end, sustained weight above the reference range is associated in BMJ meta-analysis (2020) with elevated risk of type-2 diabetes, non-alcoholic fatty liver disease, sleep apnoea, several site-specific cancers, and knee and hip osteoarthritis progression. For clinicians the number matters because it feeds directly into aminoglycoside and chemotherapy dosing algorithms, into ventilator tidal-volume settings (ARDSNet protocol, 6 ml/kg of ideal body weight), and into bariatric eligibility scoring. For a member of the public the number matters because it converts an abstract concept — "healthy weight" — into a concrete kilogram figure they can compare against the scale each week, and it does so using the same equation that a hospital pharmacist would use for the same person, so the conversation between patient and clinician can start from a shared reference. Used this way the ideal weight calculator gives clinicians and patients a shared kilogram anchor rather than a vague concept of "healthy weight." The value returned by this ideal weight calculator is therefore best treated as a shared vocabulary between patient and clinician: a number small enough to remember, precise enough to plan against, and grounded in half a century of published clinical evidence rather than in marketing or fashion.

This ideal weight calculator uses the Devine ideal body weight equation, which is deliberately simple: it uses only height and biological sex, so the number it returns is a population-level reference rather than an individualised target. Because it is derived from mid-twentieth-century clinical dosing research, several important adult populations sit outside the range where the formula behaves well and the result should be interpreted cautiously. The most important limitation of this ideal weight calculator is that it treats every adult of a given height and sex identically. Trained athletes and heavily muscled individuals routinely carry mass that this ideal weight calculator will flag as above the reference range even though their body composition is metabolically healthy; a 2019 systematic review in the BMJ Open Sport & Exercise Medicine journal recommended pairing Devine with a body-fat estimate before drawing any conclusion about excess adipose tissue in this group. Elderly adults, especially those over 70, tend to lose stature through vertebral compression and gain intra-abdominal fat while losing appendicular muscle; Cochrane analyses (2020) show that Devine can under-estimate lean-mass reserve in older women, which in turn under-estimates protein and energy requirements during recovery from surgery or illness. Children and adolescents are outside the intended scope entirely — Devine was never validated below 152 cm and its slope of 2.3 kg per inch does not describe paediatric growth curves. Pregnant and lactating women should use pregnancy-specific weight-gain guidance from the WHO 2016 antenatal care recommendations rather than Devine. The formula does not account for ethnicity, and comparative data from the JAMA Network Open (2021) suggest that reference ranges derived from primarily European clinical samples systematically over-estimate ideal weight for South and East Asian body frames and under-estimate it for Pacific Islander populations. It also does not account for amputation, orthopaedic prostheses, ascites, oedema, or major fluid shifts, all of which distort the measured height-to-weight relationship. Even within the target adult range the equation returns a single point estimate with no confidence interval, so two people of identical height and sex will get the same number even if their body composition, bone density, and activity level are radically different. For any clinical decision — drug dosing, ventilator settings, nutritional prescription, bariatric assessment — the Devine value should be used alongside, not in place of, direct measurement of weight, height, waist circumference, body composition, and where relevant biochemical markers, and the final decision should rest with a qualified healthcare professional using the current NICE, CDC, or WHO guideline appropriate to the clinical context.