BMI Calculator – What is My Body Mass Index Score?

The Body Mass Index (BMI) Calculator estimates whether your weight is in a healthy range for your height. While not a perfect measure of body composition, BMI is one of the most widely used indicators of health risk and can provide useful context for training, performance, and long-term wellbeing.

What Is BMI?

BMI is calculated using your height and weight. The result places you into a category that suggests whether your weight is under, healthy, overweight, or obese:

• Underweight: Less than 18.5
• Healthy weight: 18.5 – 24.9
• Overweight: 25 – 29.9
• Obese: 30 or more

Why Is BMI Useful?

Although BMI doesn’t measure muscle or fat directly, it offers a quick snapshot of health risk. For runners and athletes, it can be a helpful baseline when tracking training adaptations and long-term health goals.

Health Implications

Falling outside the healthy BMI range can increase the risk of certain conditions.

• Underweight: Higher chance of nutrient deficiencies, reduced immunity, and lower muscle strength.
• Overweight/Obese: Greater risk of heart disease, type 2 diabetes, joint stress, and some cancers.

Training and Fitness Insights

Staying in a healthy BMI range can support:

• Improved endurance and agility
• Less stress on joints and tendons
• Better running economy and efficiency

How BMI Affects Running

Your BMI influences efficiency, joint health, and recovery:

• Performance impact: A lower BMI can aid speed and endurance, though being too light may reduce strength and recovery. A higher BMI may add power if muscle-based, but often reduces efficiency.
• Joint health: Extra weight increases stress on knees, hips, and ankles. Staying closer to a healthy range reduces strain.
• Energy efficiency: Carrying less excess weight means each step requires less energy, boosting running economy.

How to Use the BMI Calculator

1. Enter your height (cm or inches).
2. Enter your weight (kg or pounds).
3. Select metric or imperial units.
4. Click “Calculate” to see your results instantly.

What You’ll See

• BMI Score: Your calculated value.
• Category: Underweight, healthy, overweight, or obese.
• Healthy range: The recommended weight range for your height.
• Graph: A visual display of where you fall within the range.

Benefits of a Healthy BMI for Runners

• Enhanced performance with improved economy
• Lower risk of running-related injuries
• Faster recovery between sessions
• Stronger cardiovascular health

Tips for Reaching a Healthy BMI

• Follow balanced nutrition with lean proteins, whole grains, and vegetables.
• Combine running with strength and mobility training.
• Prioritise sleep and recovery.
• Stay hydrated to support metabolism and endurance.
• Set realistic, step-by-step goals.

Limitations of BMI

BMI does not distinguish between muscle and fat, nor does it consider fat distribution. Athletes with higher muscle mass may appear overweight despite being healthy. It’s best used alongside other measures such as blood pressure, cholesterol, and overall fitness.

BMI is a starting point, not a full picture. Use the RunReps BMI Calculator to check your status, then combine the result with smart training, good nutrition, and proper recovery to support long-term performance.

Disclaimer: BMI is a general guide and should not replace professional medical advice. For personalised guidance, consult a healthcare professional.