What it is
The TDEE Calculator (external link) is a free online tool that estimates your Total Daily Energy Expenditure (TDEE) — the number of calories your body burns in a day, accounting for both resting metabolism and activity level. It works by first calculating your Basal Metabolic Rate (BMR, the calories you'd burn at complete rest) from your age, sex, height, and weight, then applying an activity multiplier based on how active you are, from sedentary to athlete-level training. Body fat percentage is an optional input that can improve accuracy. The output includes your estimated TDEE, BMR, BMI, and a macronutrient breakdown.
Why this is a useful starting point on a GLP-1
Appetite suppression makes it easy to lose track of what your body actually needs, not just what you happen to be eating. A TDEE estimate gives you a reference point — a rough sense of your baseline caloric needs — against which to evaluate whether your current intake (especially if significantly reduced by appetite suppression) is in a reasonable range, too low, or appropriate for your goals.
How it pairs with tracking
A TDEE estimate is most useful as an input to planning, not a number to hit exactly day to day:
- Use it to set a starting point for calorie and protein targets, then refine those targets with your prescriber or a dietitian — see our discussion guide on talking to a dietitian or trainer.
- Pair it with actual tracking. A TDEE calculator estimates what you need; a tool like Cronometer tracks what you're actually getting — using both together closes the loop between target and reality.
- Revisit the estimate periodically. TDEE changes as your weight changes, so a number calculated at the start of treatment won't stay accurate through significant weight loss — recalculating every so often (for example, after each 10-15 lbs lost) keeps the estimate relevant.
Benefits specific to GLP-1 users
- Counters the tendency to under-eat too aggressively. Appetite suppression can make it easy to fall well below what your body needs, especially for protein and overall nutrient adequacy (see our guide on protein, fat, and carbohydrates) — a TDEE estimate provides a sanity check against eating too little, not just too much.
- Supports body composition goals. Whether you're targeting weight loss or a body recomposition approach, knowing your baseline energy needs helps calibrate whether you're in a deficit, at maintenance, or in a surplus — a meaningfully different question from "how many calories am I eating."
- Gives you a concrete number for conversations with your care team, rather than a vague sense of "eating less."
A caution worth naming
TDEE calculators provide an estimate, not a precise measurement — individual metabolism varies, and GLP-1 medications themselves may affect energy expenditure and fat oxidation in ways a generic calculator doesn't account for. Treat the output as a reasonable starting range to work from and adjust based on real-world results, not a precise target to hit exactly.
The bottom line
The TDEE Calculator is a quick, free way to establish a baseline for how many calories and how much protein your body actually needs — a useful reference point for making sure appetite suppression doesn't lead to eating too little, and a natural pairing with detailed tracking tools like Cronometer.