Overweight Classification Calculator

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Walk-through

How to Use This Calculator

4 steps

1

Enter your height and weight

Use the unit toggle to enter your height and weight in centimetres/kilograms or inches/pounds — the calculator converts everything internally. You can also click a preset (Normal weight, Overweight, Obese Class II) to load a realistic starting point.

2

Read your classification

The headline result is your WHO weight-status tier — Underweight, Normal weight, Overweight, or Obese Class I/II/III. Below it, your BMI value and how many BMI points separate you from the next tier are shown, along with a plain-language interpretation.

3

See the BMI on its own

Open the BMI tab to see the raw BMI value and formula without the tier language, plus a comparison of how the same height can land in different tiers depending on weight.

4

Check all six tiers

The All Tiers tab lists every WHO classification band with its BMI range and what it suggests, with your current tier highlighted. This is a general screening tool, not a diagnosis — bring your result to a clinician for a fuller picture.

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Reference

Formula & Methodology

2 formulas

Body Mass Index (BMI)

BMI = weight (kg) / height (m)²

Weight in kilograms divided by the square of height in metres. This calculator converts pound and inch inputs to kilograms and metres internally before computing, so results are identical regardless of which unit system you enter.

WHO adult BMI classification

Underweight < 18.5 · Normal 18.5–24.9 · Overweight 25–29.9 · Obese I 30–34.9 · Obese II 35–39.9 · Obese III ≥ 40

The World Health Organization defines six BMI tiers for adults. This calculator classifies your BMI into one of these six tiers and reports how many BMI points separate you from the next tier in the sequence.

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YMYL

Trust, Methodology & Sources

Reviewed by Calculover Editorial Team · Updated 2026-07-23 · 2 sources

Editorial accountability

Author: Calculover Editorial Team - Editor

Owner: Calculover Editorial Team - Editorial owner

Reviewer: Calculover Editorial Team - Editorial reviewer

Last reviewed: 2026-07-23

Last verified: 2026-07-23

Data effective: 2026-07-23

Methodology

The Overweight Classification Calculator computes BMI = weight (kg) / height (m)^2 from user-entered height and weight, converting pound and inch inputs to kilograms and metres internally. The result is classified into the World Health Organization's six standard adult BMI tiers: Underweight (<18.5), Normal weight (18.5-24.9), Overweight (25-29.9), Obesity Class I (30-34.9), Obesity Class II (35-39.9), and Obesity Class III (>=40). The calculator also reports the BMI-point distance from the current tier to the next tier in the sequence.

Assumption: Height and weight are measured accurately for the same individual, with the unit system set correctly before reading the result.

Assumption: The user wants a general-population BMI screening classification, not a personalised diagnosis or a body-composition analysis.

Assumption: The WHO adult BMI cut-points apply as a general-population reference and are not adjusted for age, sex, ethnicity, or muscle mass.

Limitations & guidance

BMI does not directly measure body fat and cannot distinguish muscle mass from fat mass, so muscular or very lean individuals may be misclassified.

The WHO adult tiers used here do not adjust for age, sex, ethnicity, or pregnancy, all of which can shift where a healthy BMI sits for a specific individual.

This is a screening classification, not a diagnosis, and does not account for other health markers such as blood pressure, glucose, or waist circumference.

Professional guidance: The Overweight Classification Calculator is for health education and screening only. It is an estimate, not a diagnosis, and it is not medical advice or a substitute for assessment, diagnosis, or treatment by a qualified healthcare professional. Do not make medical decisions based on its output.

Primary sources

World Health Organization. Body mass index (BMI) and its interpretation, adult BMI classification. - World Health Organization

Centers for Disease Control and Prevention. About Adult BMI. - CDC

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Glossary

Key Terms Explained

8 terms

WHO BMI classification The World Health Organization's six-tier system for categorizing adult body weight status using BMI: Underweight, Normal weight, Overweight, and Obesity Classes I, II, and III.

Underweight A BMI below 18.5. May indicate insufficient body weight for your height, sometimes linked to nutrient deficiencies or an underlying health condition.

Normal weight A BMI from 18.5 up to (but not including) 25. Associated with the lowest average health risk in most adult populations.

Overweight A BMI from 25 up to (but not including) 30. Linked to a moderately elevated risk of conditions such as type 2 diabetes and cardiovascular disease.

Obesity Class I A BMI from 30 up to (but not including) 35. Linked to a high risk of weight-related health conditions.

Obesity Class II A BMI from 35 up to (but not including) 40. Linked to a very high risk of weight-related health conditions.

Obesity Class III A BMI of 40 or above, sometimes called severe or morbid obesity. Linked to the highest weight-related health risk category; clinical guidance is strongly recommended.

Body Mass Index (BMI) Weight in kilograms divided by height in metres squared. A simple screening measure of weight relative to height — it does not directly measure body fat and does not account for age, sex, ethnicity, or muscle mass.

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Scenarios

Real-World Examples

3 worked examples

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Jordan, 34 — average-build adult

Normal weight example

Height 175 cm Weight 70 kg BMI 22.9

Jordan's BMI of 22.9 falls in the Normal weight tier (18.5–24.9), about 2.1 BMI points below the Overweight threshold. This tier is associated with the lowest average health risk in most adult populations.

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Sam, 45 — moderately active adult

Overweight example

Height 175 cm Weight 85 kg BMI 27.8

Sam's BMI of 27.8 falls in the Overweight tier (25–29.9), about 2.2 BMI points from Obese Class I. This tier is linked to a moderately elevated risk of conditions such as type 2 diabetes and cardiovascular disease.

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Riley, 52 — managing a chronic condition

Obese Class II example

Height 175 cm Weight 115 kg BMI 37.6

Riley's BMI of 37.6 falls in the Obese Class II tier (35–39.9), about 2.4 BMI points from Obese Class III. This tier is linked to a very high risk of weight-related health conditions — a conversation with a clinician about a management plan is worthwhile.

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Deep Dive

Understanding the WHO BMI Weight Classification Tiers

3 chapters · 4 min read

This calculator classifies your Body Mass Index (BMI) into the six adult weight-status tiers defined by the World Health Organization — from Underweight through Obesity Class III. It's a fast way to see where your BMI sits on the standard scale and how far you are from the next tier, but it's a general screening tool, not a diagnosis.

How the classification works

BMI is calculated as weight in kilograms divided by height in metres squared. The World Health Organization defines six tiers along this scale: Underweight (below 18.5), Normal weight (18.5–24.9), Overweight (25–29.9), Obesity Class I (30–34.9), Obesity Class II (35–39.9), and Obesity Class III (40 and above). This calculator computes your BMI, finds which tier it falls into, and reports the distance in BMI points to the next tier in the sequence.

These are the same population-level cut-points used across the site's other BMI-based tools, and they match the WHO adult BMI classification used internationally for public-health screening.

Height and weight — what they mean here

Height should be your standing height without shoes, and weight your current body weight on a flat, level scale — ideally measured in similar clothing each time for consistency. You can enter either in metric (centimetres, kilograms) or imperial (inches, pounds) units; the calculator converts internally so the tier result is identical either way.

Because BMI depends only on the ratio of weight to height squared, the calculator is most sensitive near tier boundaries — a small weight change close to a threshold like 25 or 30 can flip your displayed tier even though your actual health status hasn't meaningfully changed.

Limits and edge cases

BMI is a screening tool, not a diagnosis, and this general-population scale does not adjust for age, sex, ethnicity, pregnancy, or high muscle mass — all of which can shift where a genuinely healthy BMI sits for a given individual. A muscular athlete, for example, can register as "Overweight" by BMI alone despite low body fat, because BMI cannot distinguish muscle mass from fat mass.

Use your tier as a starting point for a conversation with a healthcare professional, not a standalone verdict. For a shape-aware complement to BMI, see the related ABSI calculator, which factors in waist circumference.

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Questions

Frequently Asked Questions

6 questions

What are the WHO BMI tiers?+

The World Health Organization defines six standard adult BMI tiers: Underweight (below 18.5), Normal weight (18.5–24.9), Overweight (25–29.9), Obesity Class I (30–34.9), Obesity Class II (35–39.9), and Obesity Class III (40 and above).

Is this the same as a standard BMI chart?+

Yes — it uses the same WHO cut-points as a standard BMI chart, but is more granular at the high end, splitting "obese" into three separate classes (I, II, III) instead of a single catch-all category.

Does this classification apply to everyone?+

It's a general-population screening tool. It does not adjust for age, sex, ethnicity, pregnancy, or high muscle mass, all of which can affect where a healthy BMI sits for a specific individual — an athlete with high muscle mass, for example, may be classified as overweight despite low body fat.

What units does this calculator support?+

You can enter height in centimetres or inches, and weight in kilograms or pounds, using the unit toggle. Internally, the calculator converts everything to metres and kilograms before computing BMI, so the result is identical regardless of which unit system you choose.

Is this a diagnostic tool?+

No. This calculator classifies your BMI into a standard screening tier. It does not diagnose any medical condition and cannot account for individual factors like body composition, medical history, or muscle mass.

Is this medical advice?+

No. This calculator is for general health education and screening purposes only. It is not a substitute for professional medical advice, assessment, or treatment. Talk to a qualified healthcare professional about your results and any health concerns.

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