Calculators and Converters

BMI Calculator Guide: Formula, Units and Ranges

By MayreDukaan Editorial TeamPublished 15 Nov 20264 min read

Illustration: a bathroom scale, a measuring tape around a green apple, a water bottle and running shoes

Use a BMI calculator with kg and cm or pounds and feet. Understand adult WHO categories, height conversion and limits for Pakistani users.

A BMI calculator divides weight in kilograms by height in metres squared. BMI stands for body mass index: a screening measure of weight relative to height, not a diagnosis or a direct measurement of body fat. The MayreDukaan BMI calculator accepts either kilograms and centimetres or pounds with feet and inches, and shows the calculated BMI and an adult category.

If you know your weight in kg but your height as feet and inches, convert the height first. The tool does not offer a mixed kg-and-feet input mode. This guide explains the conversion, the adult categories and why the result needs context.

The BMI formula, with a checked example

The formula is BMI = weight in kg ÷ (height in metres × height in metres). If height is recorded in centimetres, divide it by 100 before squaring it.

For an adult weighing 70 kg and measuring 170 cm:

Convert 170 cm to 1.70 m.
Square the height: 1.70 × 1.70 = 2.89.
Divide 70 by 2.89 = 24.22145….
Report BMI as approximately 24.2 kg/m².

Entering 170 directly into the metres-based formula produces a dramatically wrong answer. In the tool’s metric mode, however, the field is explicitly centimetres, so enter 170 there, not 1.70. The calculator performs the centimetre-to-metre conversion internally.

How to enter your measurements

Select kg / cm for metric inputs or lb / ft-in for imperial inputs.
Enter weight and height in the units shown beside the fields.
For imperial height, enter feet and remaining inches separately.
Read the BMI, category and displayed weight range.
Check the inputs again before interpreting an unexpected result.

The calculation runs in the browser and needs positive weight and height values. It does not ask for age or sex, calculate calorie needs, or use a child growth chart. Those omissions matter: the result is not a personalised health assessment.

If you have 70 kg and a height of 5 ft 7 in, convert height to 67 inches, then multiply by 2.54 to get 170.18 cm. Enter 70 and 170.18 in metric mode. The cm and inches converter can help check that height. Alternatively, convert weight with the kg to pounds converter before using imperial mode.

Understand the adult category boundaries

WHO identifies adult underweight below 18.5, overweight at 25 or above, and obesity at 30 or above. The tool separates overweight from obesity in its displayed categories as follows.

BMI, using the unrounded result	Tool category
Below 18.5	Underweight
18.5 to below 25	Healthy weight
25 to below 30	Overweight
30 or above	Obesity

The phrase “healthy weight” is a screening label, not proof that every aspect of health is satisfactory. Likewise, a result outside that interval does not by itself establish a diagnosis or prescribe a treatment.

Near a boundary, rounding can be misleading. A value just below 25 may display as 25.0 if rounded to one decimal, although the underlying calculation remains below the threshold. Keep sufficient precision when checking category changes, rather than classifying solely from a rounded display you copied elsewhere.

What the displayed weight range means

The tool works backwards from BMI values of 18.5 and 24.9 to calculate a height-based weight interval. At 170 cm, those endpoints are 18.5 × 1.70² = 53.465 kg and 24.9 × 1.70² = 71.961 kg, or approximately 53.5–72.0 kg when rounded to one decimal place.

That interval is mathematical context, not an individual target or a recommendation to lose or gain a particular amount. The upper calculation uses 24.9 rather than the exact value immediately below 25. Ask a qualified clinician what, if anything, the result means for you before making major changes.

Limits that matter for Pakistani users

The NHS adult guidance notes that some ethnic backgrounds, including South Asian backgrounds, can have health risks at lower BMI values. The MayreDukaan tool still uses the general category boundaries above; it does not switch thresholds based on Pakistani or other ancestry.

BMI also cannot distinguish muscle from fat. An athletic build can therefore require different interpretation from a simple category label. NHS guidance advises against using its adult calculator during pregnancy or for someone with a condition affecting height. A clinician can decide which measurements are appropriate.

Children and teenagers need age-appropriate assessment rather than this adult table. WHO describes childhood classifications in relation to age, and the NHS provides a separate child and teenage calculator. Do not enter a child’s measurements here and interpret the adult label as a paediatric assessment.

Common mistakes and a sensible next step

Avoid entering feet as decimal notation: 5 ft 7 in is not 5.7 ft. Do not mix pounds with a kilogram field or metres with a centimetre field. Use consistent measurements if you are comparing results over time, and avoid treating small rounded changes as a diagnosis.

Start with the BMI calculator for the arithmetic. Keep the measured weight, height and date with your result, then discuss concerns with a healthcare professional who can interpret them alongside your wider health.

Frequently asked questions

What is the full form of BMI?

BMI means body mass index. It relates weight to height using kilograms divided by metres squared.

Can I enter kilograms and feet together?

The tool has kg/cm and lb/ft-in modes, not a mixed mode. Convert feet and inches to centimetres before entering a weight in kilograms.

Can this BMI result diagnose a health condition?

No. BMI is a screening measure and does not directly measure body fat or account for your complete health circumstances.

Are the categories suitable for children?

Not as an adult classification. Children and teenagers need age-appropriate assessment and growth references.

Useful on MayreDukaan

Sources

Facts last checked against these sources on 15 Nov 2026, 07:43 Pakistan time.

Images: Illustration created for MayreDukaan (not a photo)