How to Work Out How Many Calories You Need

Every calorie estimate starts with your Basal Metabolic Rate (BMR) — the energy your body uses at rest just to keep you breathing, pumping blood, and functioning. From there, an activity multiplier is applied to give your Total Daily Energy Expenditure (TDEE): the total calories your body uses across a full day.

The key factors involved

• Body weight and height — larger bodies generally require more energy at rest.
• Age — BMR tends to decline gradually with age.
• Biological sex — influences baseline energy needs due to differences in muscle mass and hormones.
• Activity level — from sedentary (desk-based, little exercise) through to very active (regular intense training). Honest self-assessment here makes a big difference to the accuracy of your estimate.
• Your goal — maintaining weight, losing weight gradually, or preserving muscle all call for different calorie targets.

What a typical range looks like

For general reference, many adults fall somewhere between 1,600 and 2,500 calories per day for maintenance, but this is a wide range for a reason — individual variation is significant. A modest calorie deficit (often cited in general nutrition guidance as around 300–500 kcal below TDEE) is commonly associated with gradual, sustainable weight loss, though what works for you depends on many factors your healthcare professional knows best.

How GLP-1 medicines change the picture

Many people taking Mounjaro or Wegovy find their appetite reduces noticeably, which can lead to eating far less than usual — sometimes less than is helpful for maintaining muscle, energy, and nutritional balance. Knowing roughly how many calories you are actually consuming becomes especially useful here, so you can spot when intake has dropped lower than intended and discuss it with your prescriber. You may also find it helpful to explore how to figure out the right calories to eat on a GLP-1 plan, or to dig into the broader question of working out your individual calorie needs in more detail.

Calculating a calorie target is one thing — consistently hitting it when your appetite is unpredictable is another. GLP Trackr's AI food photo scan is where most users start: point your camera at a meal and the app estimates calories, protein, and macros instantly, with no manual entry needed. It takes the friction out of logging on days when food feels like an afterthought.

Once you have a calorie target in mind (from a calculator or your healthcare professional), you can set it directly in the app as a daily goal. GLP Trackr then tracks your running total against that target throughout the day, alongside your protein and water intake — so you always know where you stand without mental arithmetic.

The weekly insights feature surfaces patterns over time: are you consistently under-eating on injection days? Is your protein intake holding steady as your weight changes? Having that data makes conversations with your prescriber or dietitian far more productive — and the app's doctor report lets you bring a clear summary to your next appointment.

For a broader look at calorie and macro tracking on a GLP-1 journey, the GLP Trackr calorie calculator hub is a good place to explore next.

General calorie ranges are educational starting points. Your individual needs depend on your health history, current medication, and goals — always follow the guidance of your prescriber or a registered dietitian before making significant changes to your eating.

Ready to stop guessing and start tracking? Download GLP Trackr on the App Store or Google Play and take it for a spin — your first 7 days are completely free.