BMR Explained: How Many Calories Does Your Body Really Need?

Your Basal Metabolic Rate (BMR) is the number of calories your body burns just to stay alive at rest — breathing, circulating blood, keeping organs running — before you take a single step. It's the foundation every calorie or diet plan is built on.

The Mifflin-St Jeor Formula

The most widely used formula today is Mifflin-St Jeor:

• Men: BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age(years) + 5
• Women: BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age(years) − 161

A Worked Example

A 30-year-old woman who weighs 65kg and is 165cm tall has a BMR of (10 × 65) + (6.25 × 165) − (5 × 30) − 161 = 650 + 1031.25 − 150 − 161 = about 1,370 calories a day at complete rest.

From BMR to Daily Calorie Needs

BMR alone isn't how many calories you should eat — it's multiplied by an activity factor (roughly 1.2 for sedentary, up to 1.9 for very active) to get your Total Daily Energy Expenditure (TDEE). Eating below your TDEE creates a deficit for weight loss; eating above it supports weight or muscle gain.

Enter your age, weight, height, and gender into our BMR calculator below to get your number instantly, along with calorie targets for maintaining, losing, or gaining weight.