An ideal weight calculator gives you an estimate of a healthy body weight for your height and sex. It's a useful reference point, but many people treat its result as a strict target and feel frustrated when their body doesn't match a single number.
This guide explains where these formulas come from, compares the four most common ones, and shows you how to turn the results into a realistic, healthy range.
Where "Ideal Weight" Formulas Come From
Most ideal body weight (IBW) formulas were created by doctors and researchers in the 1960s–1980s. Some were originally designed to help calculate medication doses, not to define how people should look.
Every ideal weight calculator relies on one of these formulas. Each formula starts with a base weight for a height of 5 feet (152.4 cm), then adds a fixed amount for every extra inch.
The Four Main Formulas
An ideal weight calculator usually shows results from these equations (weights in kg, height in inches over 5 feet):
| Formula | Men | Women |
|---|---|---|
| Devine (1974) | 50 + 2.3 per inch | 45.5 + 2.3 per inch |
| Robinson (1983) | 52 + 1.9 per inch | 49 + 1.7 per inch |
| Miller (1983) | 56.2 + 1.41 per inch | 53.1 + 1.36 per inch |
| Hamwi (1964) | 48 + 2.7 per inch | 45.5 + 2.2 per inch |
Worked Examples
A Man Who Is 5'10" (178 cm)
He is 10 inches over 5 feet.
- Devine: 50 + 23 = 73 kg
- Robinson: 52 + 19 = 71 kg
- Miller: 56.2 + 14.1 = 70.3 kg
- Hamwi: 48 + 27 = 75 kg
A Woman Who Is 5'5" (165 cm)
She is 5 inches over 5 feet.
- Devine: 45.5 + 11.5 = 57 kg
- Robinson: 49 + 8.5 = 57.5 kg
- Miller: 53.1 + 6.8 = 59.9 kg
- Hamwi: 45.5 + 11 = 56.5 kg
Notice that the formulas disagree by several kilograms. This is normal. No ideal weight calculator formula is "the right one" – each was based on different data and assumptions.
Compare With the BMI Healthy Range
Another approach is to use the healthy BMI range of 18.5–24.9 and convert it to weight for your height:
- 5'10" (1.78 m): about 58.5–78.7 kg
- 5'5" (1.65 m): about 50.4–67.9 kg
The classic formulas all land inside these ranges, usually near the middle. Many health professionals prefer thinking in ranges because healthy bodies come in many shapes.
How Frame Size Changes Your Result
People with a larger bone structure naturally weigh more at the same height. The Hamwi method suggests adjusting by about 10%:
- Small frame: subtract about 10%
- Medium frame: use the result as is
- Large frame: add about 10%
A Quick Frame-Size Check
Wrap your thumb and middle finger around your opposite wrist, just above the wrist bone:
- Fingers overlap: likely a small frame
- Fingers just touch: likely a medium frame
- Fingers don't meet: likely a large frame
This is a rough home test, but it explains why two people of the same height can both be healthy at quite different weights.
Limits of Any Ideal Weight Calculator
Keep these points in mind:
- Muscle is ignored. Athletes may weigh above the formula result while being very lean.
- Age is ignored. Some research suggests slightly higher weights may be protective in older adults.
- Ethnicity is ignored. Health risk at a given weight can differ between populations.
- Formulas are less reliable for very short or very tall people.
The Unique Value Section: Build Your Personal Target Range
Rather than chasing one number from an ideal weight calculator, combine the information an ideal weight calculator gives you into a personal range. Here's a simple method:
- Write down all four formula results. Use the lowest and highest as your formula range.
- Adjust for frame size using the wrist test.
- Check it against your BMI healthy range. Keep only the part that overlaps.
- Add a waist check. Aim for a waist measurement less than half your height.
- Consider how you feel and perform. Energy, sleep, strength, and medical markers matter more than hitting an exact figure.
For the 5'10" man with a medium frame, this gives a practical range of roughly 70–75 kg, with the waist check confirming whether that range suits his body composition.
Pro tip: If you are currently far from your range, set a first goal of losing or gaining 5–10% of your current weight. Smaller, reachable goals often bring meaningful health improvements and are far easier to maintain.
When to Talk to a Professional
Speak with a doctor or registered dietitian if:
- You have a medical condition affected by weight
- You are pregnant or breastfeeding
- You have a history of disordered eating
- Your weight has changed quickly without explanation
They can help you set targets based on your full health picture, not just a formula.
Practice: Calculate Your Own Range
Use this quick method alongside an ideal weight calculator:
- Count inches over 5 feet. Someone 5'7" is 7 inches over.
- Run two formulas. For a woman: Robinson = 49 + 1.7 × 7 = 60.9 kg; Devine = 45.5 + 2.3 × 7 = 61.6 kg.
- Adjust for frame using the wrist test.
- Check the BMI range: at 5'7" (1.70 m), that's about 53.5–72 kg.
- Settle on a personal range, for example 58–65 kg, then refine it with your waist measurement.
This takes about five minutes and gives a target range that's far more useful than any single number.
Expert Tip and Final Takeaway
An ideal weight calculator is best used as a guide, not a verdict. The four classic formulas give slightly different answers, so combine them with frame size, BMI range, and waist measurement to find a healthy range that fits your body.
Expert tip: Focus on habits you can keep for years – regular activity, balanced meals, and good sleep. When those are in place, your weight will usually settle into a healthy range on its own.
