What “ideal weight” really means (and how to use it without obsessing)

“Ideal weight” sounds like a single perfect number — but in real life, that’s not how healthy bodies work. Even for the same height, two people can have very different healthy weights depending on bone structure, muscle mass, age, training history, and medical context. So the best way to use an ideal weight calculator is to treat it like a starting map, not a final verdict.

This page combines two ideas: (1) classic ideal body weight (IBW) formulas and (2) a BMI-based healthy range. The formulas (Devine, Hamwi, Robinson, Miller) are commonly referenced in clinical and educational settings because they are fast and height-based. Historically, they were used for things like medication dosing estimates, quick screenings, and baseline targets in general populations. They are not personalized “your body’s destiny” numbers.

Each formula was created from different datasets and assumptions. They’re all “reasonable,” but none are perfect. Instead of forcing one method, we show all four and then give you an average plus the BMI healthy range. That makes your result feel less like a judgment and more like a set of useful reference points.

These classic formulas are written using inches. If you enter centimeters, we convert to inches behind the scenes: inches = centimeters ÷ 2.54. If you use feet and inches, we compute: total inches = (feet × 12) + inches.

For adults, most formulas treat 5 feet (60 inches) as the “base height.” Then they add extra kilograms for each inch above 5 feet. Here are the formulas we use:

• Devine formula (kg): Male = 50 + 2.3 × (inches − 60) · Female = 45.5 + 2.3 × (inches − 60)
• Hamwi formula (kg): Male = 48 + 2.7 × (inches − 60) · Female = 45.5 + 2.2 × (inches − 60)
• Robinson formula (kg): Male = 52 + 1.9 × (inches − 60) · Female = 49 + 1.7 × (inches − 60)
• Miller formula (kg): Male = 56.2 + 1.41 × (inches − 60) · Female = 53.1 + 1.36 × (inches − 60)

Notice how each method uses a different “per inch” increase. That’s why one formula might give you 150 lb while another gives 160 lb for the exact same height. The goal isn’t to find which one is “true” — the goal is to understand that ideal weight is a range.

If you prefer pounds, we convert using: pounds = kilograms × 2.20462. The calculator can show results in kg only, lb only, or both.

BMI (Body Mass Index) is defined as: BMI = weight(kg) ÷ height(m)². Many health references treat BMI 18.5 to 24.9 as the “healthy” adult range. Instead of giving you BMI itself, we reverse the equation to calculate the weight range that corresponds to that BMI window:

• Lower healthy weight (kg) = 18.5 × height(m)²
• Upper healthy weight (kg) = 24.9 × height(m)²

This healthy range is practical because it’s not tied to a single ideal weight formula — it’s tied to a widely used screening measure. However, BMI has limitations: very muscular people may have a higher BMI without elevated health risk, while older adults can have “normal BMI” but low muscle mass. So again: use the range as a guide, not a label.

Suppose you’re 5'9" (69 inches). The “inches above 5 feet” value is 69 − 60 = 9. Using Devine: Male: 50 + 2.3×9 = 70.7 kg (≈ 156 lb) and Female: 45.5 + 2.3×9 = 66.2 kg (≈ 146 lb). Hamwi will usually be a bit higher for men because it adds 2.7 kg per inch above 5 feet.

Now compare to BMI: height 5'9" is about 1.75 m. Height squared is about 3.06. Healthy BMI range gives: 18.5×3.06 ≈ 56.6 kg (125 lb) to 24.9×3.06 ≈ 76.2 kg (168 lb). That’s a wide range — and that’s the whole point. Healthy isn’t one number.

• If you’re starting from scratch: aim for the middle of the healthy BMI range and focus on habits.
• If you lift weights seriously: you may feel and perform best toward the upper end (or slightly above).
• If you’re optimizing endurance: you might sit lower in the range depending on sport and medical guidance.
• If the number triggers anxiety: use it only as a medical reference and focus on strength, sleep, and energy.

The best viral (and actually helpful) use of an ideal weight calculator is to pair the result with a question like: “If I aim for the middle of the range, what habits would get me there?” That shifts the conversation from self-criticism to action.

For children/teens, ideal weight should be evaluated with pediatric growth charts and clinical guidance. If you’re under 18, pregnant, dealing with eating disorders, or have medical conditions, please talk to a professional.

Frequently Asked Questions

• Is ideal weight the same as healthy weight?

  Not exactly. “Ideal weight” usually comes from a formula (or set of formulas) that estimates a typical adult body weight for a given height. “Healthy weight” is broader — it includes ranges based on BMI and other factors like muscle mass, labs, and overall health. That’s why this calculator shows both.

• Which formula should I trust: Devine or Hamwi?

  Both are widely referenced, but neither is “the truth.” They’re quick estimates created for general adult populations. If you want one simple number, use the average of all four formulas and sanity-check it against the healthy BMI range.

• Why do men and women get different results?

  The classic formulas were designed around population differences in lean mass and body composition. They use a male/female offset and per-inch increase. If you’re non-binary or your body composition differs from the average, use the results as reference points, not labels.

• What if I’m muscular and BMI says I’m “overweight”?

  BMI doesn’t distinguish muscle from fat. Many athletes and lifters fall above “normal BMI” while still being healthy. In that case, use waist measurements, strength, cardio fitness, labs, and how you feel — ideally with a clinician’s guidance.

• Is this accurate for people under 5 feet tall?

  The formulas still compute a value, but accuracy can drop because the original assumptions were centered on adult heights around and above 5 feet. If you’re significantly below 5 feet, treat the number as a rough estimate and focus more on the BMI range and clinical context.

• Can I use this for medication dosing?

  Don’t self-dose medication. Some clinicians may use ideal weight or adjusted weight in specific contexts, but dosing decisions depend on the medication, kidney/liver function, and other factors. Use this tool for education and goal-setting only.

• What’s the fastest healthy way to reach my target?

  Safe rates vary, but common guidance for fat loss is slow, consistent change with enough protein, strength training, and sleep. If you want a practical calculator stack: use a TDEE calculator to estimate maintenance calories, then a deficit calculator to plan a sustainable gap.