BMI
24.50 (Healthy Weight)
Healthy Weight Range
56.70kg - 76.30kg
Waist-to-Height
0.49 (Healthy)
Rates & sources
Body Mass Index uses weight (kg) ÷ height (m)². WHO categories apply globally.
Source: WHO — BMI classification — figures refreshed at the start of each tax year.
When to use this calculator
- Before setting a new health goal or checking whether a plan is realistic.
- When you want to compare different assumptions without tracking them manually.
- When you need a quick baseline before discussing the result with a professional.
- When you are starting a new fitness or diet programme and want an objective starting-point measurement.
- When you want to recheck your numbers after several weeks of change to see whether the metrics are moving in the right direction.
Example: using BMI as a simple first screening tool
Use these sample inputs as a quick scenario test, then change one variable at a time to compare outcomes.
Weight
80 kg
Height
178 cm
Goal
Check whether the result sits in a healthy range
Next check
Compare with waist or body-fat measures
This example shows what BMI can do well: provide a quick screening signal. It is less useful as a standalone health judgement, which is why the next comparison matters.
How to read your results
BMI
Treat BMI as a broad screening marker rather than a clinical diagnosis, and always read it alongside the other health indicators the tool produces. If the result falls outside the healthy range, discuss it with a GP before making significant changes to diet or exercise.
Healthy Weight Range
This output shows a planning range based on standard BMI thresholds, not a prescriptive personal target, so apply it with context and common sense. Use it as a reference point alongside advice from a healthcare professional rather than as a standalone goal.
Waist-to-Height
Waist measurement adds important context to a headline BMI result and can indicate metabolic risk even when overall weight appears normal. Use it alongside the other outputs to get a more complete picture before drawing any conclusions.
Method & assumptionsAuthoritative sources
Body Mass Index (BMI) is calculated by dividing your weight in kilograms by the square of your height in metres (kg/m²). It was developed in the 19th century as a statistical tool for comparing body size across populations, and it remains one of the most widely used screening metrics in public health. However, BMI was never designed as a diagnostic tool for individuals. It takes no account of age, sex, muscle mass, bone density, or fat distribution — all factors that influence health risk. Use your BMI result as a starting point for a broader conversation about health, not as a definitive verdict. A GP or registered dietitian can provide context based on your full medical history.
Common mistakes
- !Using optimistic assumptions without testing a more cautious scenario as well.
- !Comparing outputs from different tools without checking that the inputs match.
- !Treating the result as a final figure rather than a broad planning indicator.
- !Entering estimated rather than accurately measured height or weight, which can shift BMI or healthy-weight results meaningfully.
- !Interpreting a single metric in isolation instead of reading it alongside the other outputs the tool provides.
What to do next
- Rerun the calculator in six to eight weeks with updated measurements to track progress objectively.
- Use the related health calculators to build a fuller picture before discussing any changes with a professional.
- Open one of the linked guides if you want more context on what the metrics mean and how they relate to each other.
- If a result falls outside the normal range, book a GP appointment to discuss it rather than acting on the figure alone.
- Note the date alongside your results so you have a clear before-and-after record when you recheck later.
Frequently asked
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End-of-article next steps
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