Mifflin-St Jeor BMR Calculator

Summary

The Mifflin-St Jeor equation, published in 1990, is widely regarded as the most accurate formula for estimating Basal Metabolic Rate (BMR) in most adults — the calories your body burns at complete rest. This calculator multiplies your BMR by a standard activity factor to produce your Total Daily Energy Expenditure (TDEE), then shows calorie targets for weight loss, maintenance, and muscle gain. It supports both metric and imperial units and updates results instantly.

How it works

1. Select your biological sex and preferred unit system.
2. Enter your age, height, and weight.
3. Choose your typical daily activity level.
4. Click Calculate to apply the Mifflin-St Jeor formula: (10 × kg) + (6.25 × cm) − (5 × age) ± constant.
5. Your BMR and TDEE are shown alongside calorie targets for each weight goal.
6. Copy any value with the Copy button for use in a meal planner or spreadsheet.

Use cases

• Set a science-based daily calorie budget for weight loss.
• Determine maintenance calories before adjusting macros.
• Establish a calorie surplus for muscle gain.
• Understand how activity level scales your resting calorie burn.
• Compare calorie needs across different activity scenarios.
• Help clients establish calorie targets as a dietitian or personal trainer.
• Track how TDEE shifts with age or significant weight change.
• Validate calorie estimates from wearables or fitness apps.

Frequently Asked Questions