Introduction
If you’ve ever wondered how to calculate BMI, you’re not alone.
BMI (Body Mass Index) is a widely used method to assess whether your weight is healthy for your height.
In this article, we explain step by step how BMI is calculated, the BMI formula, and even the BMI equation, with examples to help you understand how to work it out yourself.
What is BMI and How is it Calculated?
BMI stands for Body Mass Index, and it is a number derived from your weight and height.
It helps categorize you as underweight, normal weight, overweight, or obese.
So, what is the BMI calculation formula?
And what is the formula for calculating BMI?
Let’s find out!
How to Calculate BMI — The Formula
The BMI formula (metric system) is: BMI=weight (kg)height (m)2BMI = \frac{\text{weight (kg)}}{\text{height (m)}^2}BMI=height (m)2weight (kg)
This is also referred to as the BMI equation, because it mathematically relates weight and height.
For example:
If you weigh 70 kg and your height is 1.75 m: BMI=701.75×1.75=703.06≈22.9BMI = \frac{70}{1.75 × 1.75} = \frac{70}{3.06} ≈ 22.9BMI=1.75×1.7570=3.0670≈22.9
Your BMI is 22.9, which falls into the “normal weight” category.
How to Calculate BMI Step by Step
Here is a clear, step-by-step guide to calculating BMI:
Step 1: Measure Your Height
Measure your height in meters (or inches).
Step 2: Measure Your Weight
Weigh yourself in kilograms (or pounds).
Step 3: Apply the Formula
Plug your numbers into the BMI formula or BMI equation.
Step 4: Interpret Your BMI
Compare your result to the standard BMI index (see the table below).
How to Calculate BMI Index
Many people ask: How to calculate BMI index?
The BMI index simply refers to the final number you get after using the formula above.
It indicates your weight category, such as:
| BMI Range | Category |
|---|---|
| Below 18.5 | Underweight |
| 18.5 – 24.9 | Normal weight |
| 25 – 29.9 | Overweight |
| 30 and above | Obese |
How Do You Calculate BMI? (Imperial Units)
If you’re using pounds and inches instead of kilograms and meters, here is how you calculate BMI: BMI=weight (lb)×703height (in)2BMI = \frac{\text{weight (lb)} × 703}{\text{height (in)}^2}BMI=height (in)2weight (lb)×703
For example:
If you weigh 154 lbs and your height is 68 inches: BMI=154×70368×68≈23.4BMI = \frac{154 × 703}{68 × 68} ≈ 23.4BMI=68×68154×703≈23.4
Common Questions About BMI Calculation
What is the BMI Calculation Formula?
It’s the same as shown earlier: weight divided by height squared (metric) or weight × 703 divided by height squared (imperial).
What is the Formula for Calculating BMI?
Metric: BMI=kgm2BMI = \frac{\text{kg}}{m^2}BMI=m2kg
Imperial: BMI=lb×703in2BMI = \frac{\text{lb} × 703}{in^2}BMI=in2lb×703
What is the BMI Calculation Formula in Words?
Your weight divided by the square of your height.
How Do You Calculate BMI Without a Calculator?
Follow the steps above with pen & paper — or use our free BMI calculator for ease.
How to Calculate BMI Equation?
Just use the mathematical formula — it’s essentially the BMI equation.
How Calculate BMI?
Whether metric or imperial, just divide your weight by your height squared — as shown above.
Why BMI Might Not Be Perfect
While BMI is a quick and useful indicator, it does not account for muscle mass, bone density, or fat distribution.
Athletes, for instance, might appear overweight by BMI standards because of their muscle.
Use Our Free Online BMI Calculator
Why do the math yourself?
Try our easy and accurate BMI calculator NHS to instantly find your BMI and category!
Conclusion
You now know how to calculate BMI, whether using the formula, equation, or step-by-step method.
Use the examples in this guide or our free calculator, and take the first step toward understanding your health better.
If you’re unsure what your BMI means, consult a healthcare provider for personalized advice.