How Many Calories Should You Eat to Lose Weight?
Published June 6, 2026
Every diet, plan, and program ever sold runs on one rule: eat fewer calories than your body burns. Here's how to find your number and how fast you can safely move the scale.
- Your TDEE (total daily energy expenditure) is your real maintenance number. Subtract from there to create a deficit.
- A 500 kcal/day deficit targets roughly 1 lb per week. A 750-1,000 kcal deficit targets up to 2 lbs.
- The old "3,500 kcal = 1 lb" rule is a starting estimate. Your metabolism adjusts as you shrink, so progress slows over time.
- Below about 1,200 kcal/day (women) or 1,500 kcal/day (men), get medical supervision.
- Protein protects muscle during a deficit and keeps you fuller on fewer calories.
BMR and TDEE: your two baselines
Before you subtract anything, you need to know your starting point.
Your Basal Metabolic Rate (BMR) is what your body burns at complete rest: pumping blood, breathing, keeping your brain and organs running. It is the largest single chunk of your daily calorie burn. The most widely used estimate is the Mifflin-St Jeor equation, which takes weight, height, age, and sex as inputs.
Your Total Daily Energy Expenditure (TDEE) adds everything else: walking, typing, exercising, digesting. BMR is multiplied by an activity factor to reach TDEE. That result is your true maintenance number, and it is what your deficit gets subtracted from.
Treat any formula output as a well-educated estimate. Individuals vary by a few hundred calories due to differences in muscle mass, genetics, hormones, and medical history.
How to read your deficit
The classic moderate cut. Matches the CDC's recommended pace of 1-2 lbs per week.
Targets ~1 lb (0.45 kg) per week.
Faster, but demands a higher maintenance level and more dietary discipline to stay nutritious.
Targets up to 2 lbs (0.9 kg) per week.
The UK’s NHS frames the same principle as a roughly 600-calorie daily reduction from your maintenance level. Either approach works; the gentler one is simply easier to hold for the months real change takes.
Why the math slows down over time
The classic rule says one pound of fat equals 3,500 calories, so a 500-calorie daily deficit burns a pound a week. As a back-of-envelope starting point, it is fine. But it treats your body like a static bank account, and it is not one.
As you lose weight, you get lighter. Your BMR falls, and you burn fewer calories doing the same things. Your body also adapts to eating less by trimming energy use in subtle ways. The practical result: progress almost always slows even when intake stays constant.
The NIH's Body Weight Planner (National Institute of Diabetes and Digestive and Kidney Diseases) uses a dynamic equation that accounts for how metabolism changes as you lose weight, giving a more realistic timeline than the 3,500-calorie rule alone.
If your progress stalls after a couple of months, you have not broken anything. Your maintenance number has dropped, and the deficit needs recalculating against your new, lighter body.
Why crash diets backfire
A severe deficit causes two problems. First, when protein intake is also low, a meaningful share of weight lost comes from lean tissue rather than fat. Less muscle means a lower resting burn, making future loss harder and future regain easier. Second, extreme restriction is difficult to sustain. Most people abandon it within weeks, often followed by a rebound that erases the loss.
A moderate deficit you can hold for six months beats an extreme one you quit in two.
The part the calculator cannot do for you
Calories decide whether you lose weight. What you eat decides whether the process is bearable. Protein is the key variable: it is the most filling macronutrient, it protects muscle during a deficit, and it costs more energy to digest than carbs or fat.
Building meals around a solid protein source, plenty of vegetables, and high-fibre foods tends to keep you satisfied on fewer calories. The Dietary Guidelines for Americans outline what a balanced pattern looks like across food groups.
Liquid calories deserve special mention. Sodas, juices, and alcohol add up quickly without filling you up, and they are an easy place to close a gap invisibly.
Adherence is the metric that actually predicts results. Low-carb, Mediterranean, plate-portioning, calorie-counting: they all work when they create a deficit you maintain, and they all fail when you cannot hold them.
Your action plan
Use the BMI Calculator for a quick benchmark of where your weight falls relative to standard ranges. The Ideal Weight Calculator gives a reasonable target band for your height. The Body Fat Calculator gets closer to body composition than scale weight alone, since the goal is almost always losing fat while keeping muscle.
This guide is for general education and isn’t medical advice. Talk to a qualified healthcare professional about your specific situation.