Adult BMI and weight range calculator
Calculate adult BMI and the weight interval corresponding to the standard adult BMI reference range.
Your inputs
Your results
Ready when you areYour results will appear here.
How it works
Calculate body mass index from weight and height, then inspect the general adult screening band and the weights corresponding to its 18.5 and 25 boundaries. The reference interval describes BMI arithmetic; it is not a prescribed ideal weight.
A few things to know
Adults 18+ only; excludes pregnancy, suspected/diagnosed eating disorders and conditions affecting height. CDC uses a different adult age boundary (20+). BMI alone cannot assess health, body composition or an individual treatment goal. No ethnicity-specific thresholds are applied; clinical interpretation can differ. Measurement bounds are input checks, not medical assessments.
When to use this tool
BMI compares body weight with height through one simple calculation. This adult BMI calculator accepts kilograms and centimetres or pounds and total inches, shows the general adult screening band, and calculates the weights corresponding to BMI 18.5 and 25. Those boundary weights explain the reference interval; they are not a personal goal or a promise of health. Use accurate measurements, check the age convention, and keep the result alongside other information rather than treating it as a diagnosis.
- Check the arithmetic behind a recorded adult BMI using your actual measurement units.
- See where an unrounded result sits relative to a screening boundary.
- Prepare the numerical result and measurement details for a conversation with a healthcare professional.
How to use adult bmi and weight range calculator
Choose units and measure
Select Metric for kg and cm, or US for lb and total inches. Enter weight and height in that selected system. A height of 5 feet 9 inches is 69 total inches.
Check the assessment scope
Enter age in whole years and select the assessment context. This calculator is for adults 18 and over, excluding pregnancy, suspected or diagnosed eating disorders, and conditions affecting height.
Read BMI with its boundaries
Compare the BMI, screening band and reference weights. The BMI 25 weight is an excluded upper boundary, and displayed numbers are rounded. Clinical interpretation can require different thresholds and other information.
70 kg at 175 cm
Inputs
Metric units; weight 70 kg; height 175 cm; age 30; adult assessment context.
Result
BMI is 22.857 kg/m², in the general healthy weight screening band. Boundary weights display as 56.66 kg at BMI 18.5 and 76.56 kg at BMI 25.
What it means
The exact reference interval is 56.65625 kg inclusive to 76.5625 kg exclusive. The tool calculates an interval for this height, rather than recommending that an individual change weight to reach it.
Common mistakes to avoid
Entering feet as a decimal
5.9 feet does not mean 5 feet 9 inches. Convert feet and inches into total inches first, or use the length converter.
Using a rounded BMI to assign the band
A value just below 25 can display as 25.000. Classification follows the full calculation, so a rounded label should not override the stated band.
Calling the interval an ideal weight
The displayed weights solve the BMI equation. They do not incorporate medical history, body composition, ethnic background or a clinician’s judgment.
Frequently asked questions
Definitions, edge cases, and practical next steps for this tool. Search all tool FAQs ↗
How does this calculator calculate BMI?
It divides weight in kilograms by height in metres squared. US inputs are first converted using 0.45359237 kilograms per pound and 2.54 centimetres per inch. For the example, 70 divided by 1.75 squared is about 22.857.
What are the general adult screening bands?
They are below 18.5, 18.5 to below 25, 25 to below 30, and 30 or above. The results table also divides the last interval at 35 and 40. These general bands are reference classifications rather than an individual diagnosis.
Is the reference weight range inclusive?
The lower BMI 18.5 boundary is included; the BMI 25 boundary is excluded. Both weights on screen are rounded to two decimal places. Use the formula rather than treating a rounded endpoint as an exact threshold for a measurement.
Can someone aged 18 or 19 use it?
This page follows the NHS adult starting age of 18. CDC uses adult BMI from age 20 and child/teen percentiles through 19. The tool highlights this difference for those ages. Follow the age convention used by the professional assessing you.
Does a healthy weight band prove I am healthy?
No. BMI is a screening measure and cannot replace an assessment that considers history, examination and other health information. A numerical band cannot identify every concern or rule out illness.
Why does the tool not ask for sex or ethnic background?
Neither changes the arithmetic of weight divided by height squared. Interpretation is a separate question. This tool applies general reference bands and does not apply ethnicity-specific clinical thresholds; use appropriate clinical guidance for that context.
Why are there measurement limits?
The accepted ranges are 100–250 cm and 20–600 kg, with equivalent US units. They catch likely unit mistakes and bound this small calculator. An input outside those limits is not a medical classification and should not be altered merely to make the form accept it.
What should I do if the result concerns me?
Check units and measurements once, then discuss the result and your circumstances with a qualified healthcare professional. Avoid turning a screening interval into an unsupervised weight-change plan. Use a suitable professional assessment when this calculator’s exclusions apply.
Explore the topic in the blog
Sources and method
Use the references below to check definitions and platform guidance. The model’s scope and limits are explained above. Read our editorial standards.