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Ideal Weight Calculator

Enter your height to compare Broca, Chinese common, WHO (BMI 22) and the BMI 18.5-23.9 range.

Setting a weight target runs into the standards themselves: one rule says height minus 105, another reverse-engineers a body-mass index, and the answers can differ by six kilograms — so which one is to be trusted? This page computes the widely used formula, the older Broca rule and the WHO figure side by side, along with the healthy weight range, so it becomes clear why the numbers differ and which of them deserves attention.

On the conventions: height minus 105 is the most widely circulated rough rule; the BMI 22 figure is the WHO's lowest-mortality weight; and the healthy range (BMI 18.5 to 23.9) is more instructive than any exact "ideal" value — being inside the range is what matters, not hitting a single number.

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How to use

  1. Enter your height.
  2. Compare the formula-based weights side by side.
  3. Check the healthy weight range for your height.
  4. Aim to sit inside the range rather than on one figure.

How it works

The four formulas

Four conventions each have a formula: the common Chinese convention = height (cm) - 105; the original Broca = height (cm) - 100; the WHO convention back-solved from the healthy BMI midpoint = 22 x height (m)^2; the healthy range = 18.5-23.9 x height (m)^2. At 170 cm the results are 65 kg, 70 kg, 63.6 kg and 53.5-69.1 kg.

Why the gap reaches 6 kg

The gap comes from the formulas' premises: Broca is a 19th-century empirical formula doing a linear height subtraction; the WHO convention treats "BMI 22" as optimal and back-solves, stricter for taller people. At 170 cm the four span about 6 kg, normal — don't worry about missing the strictest number.

Which number to look at

Judgment favors the range over a point: a BMI in 18.5-23.9 (China's adult standard) can be considered a healthy weight range, combined with body fat, waist circumference (men < 90 cm, women < 85 cm) and muscle mass. Gym-goers with high muscle and normal body fat are healthy despite a higher BMI.

Calculation basis: Broca's original formula (height − 100), the common Chinese reference (height − 105) and the mid-point of the WHO-recommended healthy BMI range (22); the healthy range uses BMI 18.5–23.9 from China's health standard WS/T 428-2013. The formulas can differ by several kilograms, so treat these as reference ranges only.

Code example

JavaScript Four ideal-weight formulas 

function idealWeights(hCm) {
  const m = hCm / 100;
  return {
    cn: hCm - 105,                       // the simple Chinese formula
    broca: (hCm - 100) * 0.9,            // Broca (men)
    who: 22 * m * m,                     // WHO, from a BMI of 22
    range: (18.5 * m * m).toFixed(1) + "~" + (23.9 * m * m).toFixed(1)
  };
}

idealWeights(170);   // range "53.5~69.1kg"

Python The same four formulas in Python 

def ideal_weights(h_cm):
    m = h_cm / 100
    return {"cn": h_cm - 105, "broca": (h_cm - 100) * 0.9,
            "who": 22 * m * m,
            "range": (round(18.5 * m * m, 1), round(23.9 * m * m, 1))}

ideal_weights(170)   # range (53.5, 69.1)

FAQ

Why do the conventions differ so much?

Different premises: Broca does only a linear height subtraction, while the WHO convention back-solves from BMI 22 and is stricter for taller people. At 170 cm the three differ by about 6 kg, normal — don't fixate on the strictest number.

Which convention should Chinese people look at?

Prioritize the BMI range (18.5-23.9). China's adult overweight and obesity cutoffs (24 / 28) are below the West's (25 / 30), so applying WHO's BMI 25 directly is too lenient for Chinese people.

Is hitting the target the only way to be healthy?

No. Weight is a single metric; also consider body fat, waist circumference and muscle mass. Those with high muscle have a higher BMI but normal body fat and are equally healthy; conversely a normal weight with an oversized waist (more visceral fat) carries higher risk.

Is the height-minus-105 convention scientific?

It's empirical, fitted to population averages, with clear errors for very tall or very short people, so it's only a range reference, not a hard target.

Does it apply to older adults?

The convention doesn't distinguish age. For older adults, being moderately heavier is often linked to better nutritional status and prognosis, so don't force weight loss by younger people's ranges — combine with a doctor's assessment.

Can children use this?

No. Children should be assessed by age- and sex-specific growth percentile curves (use this site's child growth tool); adult ideal-weight formulas don't apply to minors.

Is my height data recorded?

No. Height is used only for local formula application, not sent or stored; the site does no user identification and has no endpoint aggregating the data. History stays in your browser and is clearable anytime.