Ideal Weight Calculator
Find your ideal body weight using four established formulas: Devine, Robinson, Miller, and Hamwi, with frame size adjustment.
Results
Visualization
How It Works
Ideal body weight (IBW) formulas estimate a healthy target weight based on height and gender. Four classic formulas are commonly used: Devine (1974), Robinson (1983), Miller (1983), and Hamwi (1964). Because each was developed for a different purpose and population, comparing all four gives a more reliable range than relying on any single formula.
The Formula
Variables
- IBW — Ideal Body Weight in kilograms
- inches over 5ft — Height in inches above 60 inches (152.4 cm)
- Frame adjustment — Multiplier: 0.9 for small frame, 1.0 for medium, 1.1 for large
Worked Example
A 170 cm male with medium frame: inches over 60 = (170 - 152.4) / 2.54 = 6.93. Devine = 50 + 2.3*6.93 = 65.9 kg. Robinson = 52 + 1.9*6.93 = 65.2 kg. Miller = 56.2 + 1.41*6.93 = 65.97 kg. Hamwi = 48 + 2.7*6.93 = 66.7 kg. Average = 66.0 kg.
Methodology
Multiple formulas have been developed to estimate ideal body weight, each with different assumptions and applicable populations. The Devine formula (1974) was originally created for calculating drug dosages based on height and was never intended as a weight management tool, yet became widely adopted: for men, IBW = 50 + 2.3 × (height in inches - 60), and for women, IBW = 45.5 + 2.3 × (height in inches - 60). The Robinson formula (1983) produces slightly different values: men IBW = 52 + 1.9 × (height in inches - 60), women IBW = 49 + 1.7 × (height in inches - 60). The Miller formula (1983) gives: men IBW = 56.2 + 1.41 × (height in inches - 60), women IBW = 53.1 + 1.36 × (height in inches - 60). The Hamwi formula (1964) uses a simpler approach: men 106 lbs for the first 5 feet plus 6 lbs per additional inch, women 100 lbs for the first 5 feet plus 5 lbs per additional inch. None of these formulas account for body composition, bone structure, or ethnic differences, which is why modern practitioners often prefer using BMI-based healthy weight ranges instead.
When to Use This Calculator
Pharmacists and physicians use ideal body weight formulas to calculate weight-based medication dosages for drugs with narrow therapeutic indices, where using actual body weight in obese patients could lead to overdosing. Individuals starting a weight loss journey use ideal weight calculations to set realistic long-term goals, though the target should be personalized based on body frame, muscle mass, and overall health rather than any single formula. Insurance companies historically used ideal weight tables to determine coverage eligibility and premium rates, though this practice has largely been replaced by BMI-based assessments. Bariatric surgery programs use ideal body weight to calculate the percentage of excess weight loss after procedures like gastric bypass or sleeve gastrectomy, which is the standard metric for evaluating surgical outcomes.
Common Mistakes to Avoid
Treating ideal weight as a single number rather than a range of 10-15 pounds is unrealistic and can promote unhealthy fixation on a specific scale reading. Relying on formulas developed decades ago on narrow population samples without considering modern body composition differences can produce targets that are too low for muscular individuals or those with larger frames. Ignoring the difference between small, medium, and large body frames when using height-based formulas can result in targets that are inappropriate for your skeletal structure. Setting a goal weight below what you weighed as a healthy young adult may be unrealistic due to age-related changes in bone density and muscle distribution.
Practical Tips
- These formulas were designed for adults over 152 cm (5 feet) tall; they are less reliable for shorter individuals. Individual nutritional needs vary based on age, sex, activity level, and health status, so use these results as a starting point and adjust based on your body's response.
- Frame size matters: wrap your thumb and middle finger around your wrist. If they overlap, you have a small frame; if they touch, medium; if a gap remains, large.
- Ideal weight formulas do not account for muscle mass. A fit, muscular person may healthily weigh more than the formula suggests.
- Use the average of all four formulas as your target rather than any single one. Individual nutritional needs vary based on age, sex, activity level, and health status, so use these results as a starting point and adjust based on your body's response.
- These formulas provide a reference point, not a strict goal. Health markers like blood pressure and blood sugar matter more than a number on the scale.
- Track your measurements consistently at the same time of day, ideally first thing in the morning before eating or drinking, to minimize natural daily fluctuations that can obscure genuine trends in your data over time.
- Use this calculator as one component of a comprehensive health assessment rather than as a standalone diagnostic tool, since no single metric captures the full picture of metabolic health, fitness, or nutritional status.
- Recalculate your values every 4 to 6 weeks when actively pursuing health or fitness goals, as changes in body composition, activity level, and metabolic adaptation require updated inputs for accurate results.
- Consult a registered dietitian or healthcare provider before making significant dietary changes based on calculator results, especially if you have pre-existing medical conditions, food allergies, or take medications that affect metabolism.
- Consider the limitations of population-based formulas when applying results to your individual situation, since genetic variation, hormonal status, medication use, and other personal factors can cause your actual values to differ from calculated estimates by 10 to 15 percent.
- Keep a log of your calculator inputs and results over time to identify trends and patterns that single-point measurements cannot reveal, such as seasonal variations in activity level or gradual changes in body composition.
- Track your measurements consistently at the same time of day, ideally first thing in the morning before eating or drinking, to minimize natural daily fluctuations that can obscure genuine trends in your data over time.
- Use this calculator as one component of a comprehensive health assessment rather than as a standalone diagnostic tool, since no single metric captures the full picture of metabolic health, fitness, or nutritional status.
- Recalculate your values every 4 to 6 weeks when actively pursuing health or fitness goals, as changes in body composition, activity level, and metabolic adaptation require updated inputs for accurate results.
- Consult a registered dietitian or healthcare provider before making significant dietary changes based on calculator results, especially if you have pre-existing medical conditions, food allergies, or take medications that affect metabolism.
- Consider the limitations of population-based formulas when applying results to your individual situation, since genetic variation, hormonal status, medication use, and other personal factors can cause your actual values to differ significantly from calculated estimates.
- Keep a log of your calculator inputs and results over time to identify trends and patterns that single-point measurements cannot reveal, such as seasonal variations in activity level or gradual changes in body composition.
- Remember that weight management is ultimately governed by energy balance, and small consistent changes to intake and expenditure compound over weeks and months into significant results that crash diets and extreme measures cannot sustain.
- Hydration status significantly affects many body composition measurements including weight, body fat percentage, and BMI, so standardize your measurement conditions to minimize this source of variability.
- Use multiple measurement methods and calculators to get a more complete picture of your health status, since each tool captures different aspects and no single metric tells the whole story.
- Avoid making dramatic dietary or exercise changes based on a single calculation result, instead using trends across multiple measurements over weeks to guide gradual, sustainable adjustments.
- Share your calculator results with your healthcare provider during routine visits to facilitate informed conversations about your health goals and appropriate interventions.
- Remember that the goal of nutrition calculations is to inform better decisions, not to create anxiety or obsessive tracking, so maintain a healthy relationship with the numbers.
- Account for individual variation by treating calculator results as starting points that you refine based on how your body actually responds over a period of consistent effort.
Frequently Asked Questions
Which ideal weight formula is the most accurate?
No single formula is definitively best. The Devine formula is most commonly used in clinical settings for drug dosing, while Robinson and Miller tend to give slightly lower estimates. Averaging all four provides the most balanced target for general health purposes.
Why do the formulas give different results?
Each formula was developed using different populations and for different purposes. Devine's was originally for calculating medication dosages, Hamwi's for quick clinical estimates. The variations typically span 2-5 kg, reflecting the natural range of healthy weights.
Does frame size really matter?
Yes, skeletal frame size affects how much you should weigh. A large-framed person has heavier bones and can carry more weight healthily. The 10% adjustment for small and large frames is a well-accepted clinical approximation.
Are these formulas appropriate for all ages?
These formulas were developed for adults. For children and adolescents, growth charts and BMI-for-age percentiles from the CDC or WHO are more appropriate. Older adults may also benefit from slightly higher weight targets, as mild overweight is associated with better outcomes in those over 65.
My current weight is far from the ideal. What should I do?
Consult a healthcare provider before making major changes. A safe rate of weight loss is 0.5-1 kg per week. Focus on sustainable dietary changes and regular physical activity rather than crash diets. Even a 5-10% reduction from your current weight can significantly improve health markers.
How often should I recalculate my values?
Recalculate every 4 to 6 weeks if you are actively pursuing health or fitness goals, or whenever you experience a significant change in weight, activity level, or health status. Body composition and metabolic rate change over time, so using outdated inputs produces results that no longer reflect your current situation and may lead to suboptimal dietary or exercise decisions.
Can I use this calculator if I have a medical condition?
This calculator provides general estimates based on population-level research and is not a substitute for individualized medical advice. If you have diabetes, kidney disease, thyroid disorders, eating disorders, or other conditions that affect metabolism or nutritional requirements, consult your healthcare provider before making changes based on calculator results. Medical conditions can cause your actual values to deviate significantly from formula-based estimates.
How accurate are the results from this calculator?
Population-based formulas used in this calculator are typically accurate to within 10 to 15 percent for most healthy adults who fall within the standard demographic ranges used to develop the equations. Accuracy decreases for individuals at the extremes of the height, weight, age, or activity spectrum, as well as for those with medical conditions or genetic variations that affect metabolism. Use the results as a reasonable starting point and adjust based on your actual outcomes over several weeks.
How often should I recalculate my values?
Recalculate every 4 to 6 weeks if you are actively pursuing health or fitness goals, or whenever you experience a significant change in weight, activity level, or health status. Body composition and metabolic rate change over time, so using outdated inputs produces results that no longer reflect your current situation and may lead to suboptimal decisions.
Can I use this calculator if I have a medical condition?
This calculator provides general estimates based on population-level research and is not a substitute for individualized medical advice. If you have diabetes, kidney disease, thyroid disorders, eating disorders, or other conditions affecting metabolism, consult your healthcare provider before making changes based on results.
How accurate are the results from this calculator?
Population-based formulas are typically accurate to within 10 to 15 percent for most healthy adults. Accuracy decreases for individuals at the extremes of height, weight, age, or activity, as well as those with medical conditions. Use results as a starting point and adjust based on your actual outcomes over several weeks.
What is the best way to track progress using these calculators?
Take measurements weekly at the same time under the same conditions, enter them into the relevant calculators, and record both inputs and outputs in a spreadsheet or journal. Look at 4-week moving averages rather than individual data points to identify meaningful trends while filtering out the normal day-to-day variation that obscures real progress.
How should I adjust my calculations for age-related changes?
Metabolic rate naturally decreases with age at approximately 1 to 2 percent per decade after age 20, primarily due to decreased muscle mass. Update your age input in calculators regularly and consider that activity level descriptions may need adjustment as your baseline activity changes. Resistance training can partially offset age-related metabolic decline by preserving muscle mass.
Are these calculators appropriate for athletes or very active individuals?
Standard formulas may underestimate needs for highly active individuals because the activity multipliers were developed from general population data. Athletes with high training volumes should consider using sport-specific calculators or working with a sports dietitian who can adjust formulas based on training load, competition schedule, and performance data.