What is BMI and why is it important to know?

BMI (Body Mass Index) is a simple calculation that compares your weight to your height. The result falls into standard categories:

• Underweight (below 18.5)

• Healthy weight (18.5–24.9)

• Overweight (25–29.9)

• Obese (30 or higher).

It’s not a perfect measure. BMI doesn’t distinguish between muscle and fat or account for body shape, but it’s a quick way to get a general sense of where your weight stands in relation to your height.

BMI works together with other measures like BMR and TDEE. BMR (Basal Metabolic Rate) is the number of calories your body needs just to function, while TDEE (Total Daily Energy Expenditure) adds in your daily activity and gives you the best estimate of how many calories you burn in a day. Put simply: BMI shows where you are in terms of body size, while BMR and TDEE show how much energy your body uses.

Knowing your BMI helps set context for your goals. If your BMI is high, pairing that knowledge with your TDEE helps you find the right calorie deficit for weight loss. If it’s low, understanding your BMR and TDEE can guide safe weight gain. And if you’re in the healthy range, you can use TDEE to maintain while focusing on balanced nutrition.

Welling is an AI weight loss coach that uses your TDEE and your BMR and automatically sets your daily targets, whether your goal is to lose, gain, or maintain weight. Through a simple AI chat, it then tracks your calories and analyzes your diet so you know exactly how to reach your goals.