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BMI-Based Weight Range Calculator

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Enter your height and current weight to see the body-weight range corresponding to standard adult BMI reference values, plus your current BMI and how it compares with that reference range.

Your details

This calculator is designed for adults aged 18 and over. Children and teenagers are assessed against age- and sex-specific growth references instead.

BMI-based reference weight range
53.5 kg – 72.0 kg
Lower BMI reference weight
53.5 kg
Upper BMI reference weight
72.0 kg
Calculated BMI
24.2
Current weight relative to BMI reference range
Within BMI reference range

Screening estimate only. This range is calculated from adult BMI values of 18.5 to 24.9 and is not a diagnosis or a personal target. BMI does not distinguish muscle from fat and may be less useful for people who are very muscular, pregnant or under 18.

For general information only. Consider other measures, such as waist-to-height ratio, alongside advice from a qualified healthcare professional where appropriate.

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How to use this calculator

  1. Enter your height, and pick its unit — centimetres, metres, feet, inches, or feet and inches.
  2. Enter your current weight, and pick its unit — kilograms, pounds, or stones and pounds, so the calculator can compare it with the reference range.
  3. Read the lower and upper BMI reference weight above, along with your BMI and where your current weight sits relative to the range.

This calculator is designed for adults aged 18 and over. Nothing is submitted anywhere. The calculation runs in the page as you type, and the link in your address bar carries your figures, so it can be shared or bookmarked.

What do I need to enter?

  • Height — from 130 cm to 220 cm, or the equivalent in metres, feet, inches or feet and inches (the inches box takes 0 to 11). It sets the size of the reference range.
  • Current weight — from 30 kg to 300 kg, or the equivalent in pounds or stones and pounds (the pounds box takes 0 to 13). It is used for your BMI and for the comparison, not for the range itself.

What do the results show?

  • BMI-based reference weight range — the main figure: the weights at your height that give a BMI from 18.5 to 24.9.
  • Lower and Upper BMI reference weight — the two ends of that range, shown in the weight unit you chose.
  • Calculated BMI — your current weight divided by your height squared.
  • Current weight relative to BMI reference range — a neutral badge: within the range, or how far below or above it your weight sits.

How this calculator works

  1. Your height and weight are converted to metric units — metres and kilograms.
  2. Your current BMI is calculated as weight in kilograms ÷ height in metres squared.
  3. The BMI formula is reversed to find the body weights that correspond to BMI 18.5 and BMI 24.9 for your height.
  4. Your current weight is compared with that interval and described in neutral terms — below, within or above the BMI reference range.

The displayed range is a BMI-based reference interval, not a personal medical target. Muscle mass, pregnancy, age, ethnicity and other individual factors are not reflected in BMI, so a weight inside or outside the range is not a statement about your health.

BMI = Weight in kg ÷ Height in metres2
Lower BMI reference weight (kg) = 18.5 × Height in metres2
Upper BMI reference weight (kg) = 24.9 × Height in metres2
  • Lower BMI reference weight — the formula run at BMI 18.5.
  • Upper BMI reference weight — the formula run at BMI 24.9.
  • Unrounded values are used throughout; only the results on screen are rounded.

Worked example. At 170 cm (1.70 m), the BMI reference range runs from 18.5 × 1.70² = 53.5 kg to 24.9 × 1.70² = 72.0 kg. A current weight of 80 kg is 8.0 kg above that range, at a BMI of 27.7.

BMI-based weight range vs. BMI vs. ideal weight

All three tools compare height and weight, but answer different questions. The BMI calculator takes a specific height and weight and tells you which category the result falls into. This calculator works in the other direction: from height alone, it shows the whole span of weights inside the BMI reference interval. The ideal weight calculator compares seven height-based reference formulas, showing each estimate, their spread and their average.

Because every figure here comes from height and weight alone, none of the three can tell the difference between a muscular, large-framed body and one carrying excess fat at the same weight. Treat the range as a reference point, not a personal target to hit.

Limitations of a BMI-based weight range

  • Uses only height and weight — it does not account for muscle mass, frame size, age or ethnicity.
  • Designed for adults. The 18.5–24.9 interval is not appropriate for children or teenagers.
  • BMI may be less useful for people who are very muscular, pregnant or under 18.
  • It is a screening reference, not a diagnosis, a body-composition assessment or medical advice.

This range is for general information only. Consider other measures, such as waist-to-height ratio, alongside advice from a qualified healthcare professional where appropriate. Waist-to-height ratio is another screening measure, not a diagnostic test in itself.

Sources

The BMI formula follows the NHS adult BMI calculator guidance and the WHO obesity and overweight fact sheet, which defines BMI as weight in kilograms divided by height in metres squared and puts overweight at a BMI of 25 or more.

Frequently asked questions

What does "BMI-based reference weight range" mean?

It is the span of body weight that corresponds to a body mass index of 18.5 to 24.9 for your height — the standard adult BMI reference interval used by the NHS and WHO. The calculator reverses the BMI formula at each end of that interval to give a lower and an upper weight. It is a population-level screening reference, not a personal target.

Is this my ideal or healthy weight?

No. This calculator does not diagnose health and does not determine the weight that is personally appropriate for you. It only shows the weights that fall inside the adult BMI reference interval for your height. BMI ignores muscle, fat distribution, age, ethnicity and many other factors, so a weight inside or outside this range is not a verdict on your health.

How is the BMI-based weight range calculated?

Body mass index is weight in kilograms divided by height in metres squared. Rearranging that formula for weight, at a fixed BMI, gives a weight for any height. This calculator runs it twice — once at BMI 18.5 and once at BMI 24.9 — to get the lower and upper bounds. Height and weight are converted to metric units first, and only the displayed figures are rounded.

Why 18.5 and 24.9, not 18.5 and 25?

The NHS and WHO define the adult BMI reference interval as 18.5 up to but not including 25, so 24.9 is the highest value that still falls inside it. This calculator and the BMI calculator use the same thresholds, so the two agree.

Why can BMI be less useful for muscular people or during pregnancy?

BMI uses only height and weight, so it cannot tell muscle from fat. A very muscular person can sit above the reference range while carrying little excess fat, and someone with low muscle mass can sit inside it while carrying more. During pregnancy, body weight rises for reasons the adult BMI reference interval was never designed to describe, so the range is not a meaningful comparison. The calculator does not produce a separate pregnancy interpretation.

Does this range depend on sex?

No. BMI and its reference interval are calculated the same way for men and women, so this calculator only needs your height — sex does not change the result.

Is this calculator suitable for children or teenagers?

No. The 18.5–24.9 interval is an adult BMI classification. Children and teenagers are assessed against age- and sex-specific growth references instead. For concerns about a child or young person’s growth or weight, speak with a GP, school nurse or another qualified health professional.

How is this different from the BMI calculator?

The BMI calculator takes your height and weight and tells you which standard adult BMI category the result falls into — Underweight, Healthy weight, Overweight or Obesity. This calculator works the other way round: from your height alone, it shows the range of weights that fall inside the BMI reference interval. Use the BMI calculator to check a specific weight, and this one to see the whole reference band at a glance.

Last updated 26 October 2026. Sources: NHS: Calculate your body mass index (BMI) for adults, WHO: Obesity and overweight.