Ideal Weight Calculator

Ideal Weight Calculator

“Ideal weight” is not a single number — it is a range that shifts based on height, gender, frame size, and body composition. This calculator runs four established medical formulas simultaneously — Devine, Robinson, Miller, and Hamwi — and also shows your healthy BMI weight range (18.5-24.9) for your height. Seeing all five outputs together gives you a realistic target window instead of chasing an arbitrary number that may not fit your body type. Use the results as a directional guide, and consult a healthcare provider to factor in your individual health history.

How Ideal Weight Is Calculated

All four formulas follow the same structure: a base weight for the first 5 feet of height, then an added amount per inch above that. The formulas were developed independently and use different base weights and per-inch increments:

The healthy BMI range uses a different approach: it converts the BMI range of 18.5-24.9 into a weight range for your specific height using the formula: weight (lbs) = BMI x (height in inches)^2 / 703. This range is typically much wider than the formula estimates and is often the most practically useful reference.

Worked Examples

Example 1 — Average-height woman near her goal. Sandra is 5’5” (65 inches), currently weighing 148 lbs, and wants to know a realistic target. The four formula results for a 5’5” woman range from 125 lbs (Devine) to 133 lbs (Robinson), with an average around 128 lbs. The healthy BMI range for 5’5” is approximately 111-149 lbs. At 148 lbs she is technically within the healthy BMI range, so a modest goal of reaching 135-140 lbs — the upper portion of the formula estimates — is realistic and health-supportive without being unnecessarily aggressive.

Example 2 — Muscular man above the formula estimates. Trevor is 5’11” and weighs 210 lbs with 11% body fat from years of powerlifting. The four formulas put his ideal weight at 163-170 lbs, and the healthy BMI range caps at 179 lbs — yet he is clearly healthy. This is a case where body fat percentage (11%) tells a better story than the formula outputs. The formulas were derived from average population data and do not account for high lean mass. His practical “ideal” is simply maintaining his current composition.

Example 3 — Older man setting a weight loss goal. Henry is 68 years old, 5’9” (69 inches), and weighs 218 lbs. The four formulas give a range of 149-163 lbs for a 5’9” male, and the healthy BMI range runs 125-169 lbs. Starting with a goal of losing 5-10% of his current body weight (about 11-22 lbs) is a more actionable first step than trying to reach 155 lbs all at once. Research shows that a 5-10% weight reduction produces meaningful improvements in blood pressure, blood sugar, and joint health even without reaching the formula target.

Reference Table

When to Use This Calculator

• Setting an initial weight loss goal — gives you a specific target range instead of a vague “I want to lose some weight” starting point
• Checking whether your current goal is realistic — if you are 5’9” and targeting 130 lbs, the formulas and BMI range both indicate that is below healthy; this calculator flags that
• Adjusting goals after significant weight change — if you have already lost 30 lbs, use the calculator to see how much further you are from the healthy range and reassess whether continuing is appropriate
• Understanding your body relative to population norms — the formulas reflect what has been associated with good health outcomes in large studies, giving you a reference point even if you ultimately set your goal slightly above or below it
• Medication dosing reference — the Devine formula in particular is used in clinical settings for weight-based drug dosing; understanding your ideal body weight (IBW) in this sense can be useful context when discussing prescriptions with a healthcare provider

Common Mistakes to Avoid

1. Treating one formula result as “the answer.” The four formulas can differ by 15-20 lbs for the same person. No single formula is definitively correct — they reflect different populations and assumptions. Use the average of all four, or use the healthy BMI range, as your reference window rather than anchoring on one number.

2. Ignoring body composition. A 185-lb person at 10% body fat and a 185-lb person at 30% body fat have the same scale weight but completely different health profiles. The formulas cannot distinguish between them. If you lift weights regularly or have significant muscle mass, your healthy weight may be above what the formulas suggest — and that is perfectly fine.

3. Setting a goal at the bottom of the range. People who target the low end of ideal weight formulas often end up either underweight or struggling to maintain a weight that requires extreme restriction. A weight at the middle or upper end of the healthy range that you can sustain without obsessive dieting is more valuable than hitting a formula floor.

4. Applying adult formulas to children or adolescents. These formulas are validated for adults only. For individuals under 18, BMI-for-age charts from pediatric growth references are the appropriate tool. Consult a pediatrician rather than using adult ideal weight calculators.

Understanding Your Results

The output of this calculator is best read as a range, not a target number. The four formulas typically produce results within about 15-20 lbs of each other, and the healthy BMI range is broader still — often spanning 35-45 lbs. This spread reflects real biological variation in healthy human bodies.

A useful practical approach: find the average of the four formula results (your “formula midpoint”) and compare it to the healthy BMI range. If the formula midpoint falls inside the BMI range, use the area between them as your realistic goal window. If the formulas are inconsistent, the healthy BMI range is the more defensible target.

These calculators do not account for bone density, organ size, edema, or metabolic health — factors a clinician can assess. If you are more than 30 lbs outside the healthy BMI range, a conversation with a healthcare provider about a structured plan is worth having before committing to a DIY approach.

Tips

1. Average the four formula results to get a midpoint, then compare that midpoint to the healthy BMI range — your realistic goal window is typically between these two references
2. If you train with weights, your ideal weight likely falls at the upper end or 5-10 lbs above the formula averages due to additional lean mass
3. Start with a 5-10% reduction from your current weight as an initial goal — this is clinically meaningful for most health markers and far more achievable than jumping straight to the formula target
4. Focus on body fat percentage alongside scale weight — reaching a formula target while carrying high body fat means less than being slightly above the target with low body fat
5. Frame size matters: if your thumb and middle finger overlap when wrapped around your wrist, you likely have a small frame; if they just touch, medium; if they do not touch, large — a large frame adds 5-10% to a realistic healthy weight
6. Weigh yourself under consistent conditions (morning, before eating, same clothing) and average the readings over a week for a more accurate picture of your true weight trend