When assessing weight and health, two commonly used measurements are Body Mass Index (BMI) and Body Fat Percentage (BFP). While both methods aim to determine whether a person is within a healthy weight range, they measure different aspects of body composition.
BMI calculates whether your weight is appropriate for your height.
Body Fat Percentage determines how much of your body is composed of fat.
This guide explains the differences, benefits, and limitations of each measurement and which one is more accurate for assessing overall health.
Body Mass Index (BMI) is a measurement that assesses weight relative to height. It is used by the NHS and World Health Organization (WHO) to classify individuals into weight categories:
✔ Underweight
✔ Healthy weight
✔ Overweight
✔ Obese
Learn more: What is BMI?
BMI is determined using the following formulas:
Metric Formula:
BMI = Weight (kg) ÷ Height (m²)
Imperial Formula:
BMI = (Weight (lbs) ÷ Height (inches²)) × 703
| BMI Range | Category | Health Risk |
|---|---|---|
| Below 18.5 | Underweight | Risk of malnutrition, weakened immunity |
| 18.5 – 24.9 | Healthy Weight | Lowest health risk |
| 25 – 29.9 | Overweight | Increased risk of heart disease, high blood pressure |
| 30 and above | Obese | High risk of diabetes, stroke, joint problems |
Find out where you stand: NHS BMI Chart
Body Fat Percentage (BFP) measures the proportion of fat in your body compared to total body weight. Unlike BMI, which does not differentiate between fat and muscle, BFP gives a direct assessment of fat levels.
There are several ways to measure BFP, including:
✔ Skinfold Calipers – Measures fat thickness at specific body sites.
✔ Bioelectrical Impedance Analysis (BIA) – Uses electrical signals to estimate fat levels.
✔ Dual-Energy X-ray Absorptiometry (DEXA Scan) – A precise but expensive method.
✔ Hydrostatic Weighing – Measures body composition using water displacement.
| Category | Men’s Body Fat % | Women’s Body Fat % |
|---|---|---|
| Essential Fat | 2 – 5% | 10 – 13% |
| Athletes | 6 – 13% | 14 – 20% |
| Fitness | 14 – 17% | 21 – 24% |
| Acceptable | 18 – 24% | 25 – 31% |
| Obese | 25%+ | 32%+ |
Want to assess your body composition? Start with BMI first: Check Your BMI Now
| Factor | BMI | Body Fat Percentage (BFP) |
|---|---|---|
| What it measures | Weight relative to height | Fat mass relative to total body weight |
| Accuracy | Does not differentiate between fat and muscle | Directly measures body fat |
| Best for | General weight classification | Detailed body composition analysis |
| Limitations | May misclassify muscular individuals as overweight | Requires special tools for accurate measurement |
✔ Quick and easy to calculate – No special equipment needed.
✔ Used in public health research – Helps track obesity trends.
✔ Standardised NHS measurement tool.
Check your BMI today: Calculate Your BMI
Does not differentiate between fat and muscle – Athletes may be classified as overweight.
Does not measure fat distribution – Central obesity (excess belly fat) is more dangerous than overall body fat.
Read more: How Accurate is BMI?
✔ More accurate for athletes and highly active individuals.
✔ Ideal for tracking fat loss rather than just weight loss.
Requires specialised equipment – Not as simple as BMI.
Accuracy varies depending on the measurement method used.
✔ You need a quick, general health indicator.
✔ You want to compare your weight with NHS guidelines.
✔ You do not have access to body fat measurement tools.
✔ You are an athlete or have high muscle mass.
✔ You want to track fat loss instead of just weight loss.
✔ You have concerns about central obesity or fat distribution.
Not always. BMI estimates weight status but does not differentiate between muscle and fat.
Bioelectrical Impedance Scales, DEXA Scans, or Calipers provide the most reliable readings.
Body Fat Percentage is better for tracking fat loss rather than just weight loss.
✔ Check your weight classification using the NHS BMI Calculator.
✔ Get instant results based on NHS guidelines.
