Calorie Deficit Calculator

What Is a Calorie Deficit?

A calorie deficit means you consume fewer calories each day than your body burns. When your body doesn't get enough energy from food, it turns to stored body fat as a fuel source, which causes you to lose weight over time.

One pound of body fat contains roughly 3,500 calories of stored energy. To lose one pound per week, you need an average daily deficit of 3,500 ÷ 7 = 500 calories.

How the Calculator Estimates Your TDEE

Your Total Daily Energy Expenditure (TDEE) is the total number of calories you burn in a day. The calculator estimates it in two steps:

1. Resting Metabolic Rate (RMR) — calories your body burns at complete rest, calculated using the Mifflin-St Jeor equation, which is the standard recommended by the Academy of Nutrition and Dietetics.
2. Activity Multiplier — your RMR is multiplied by a factor that accounts for how active you are each week.

The Mifflin-St Jeor equation is:

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

If you want a more precise measurement, use the TDEE Calculator which offers additional body-composition inputs, or check the manual override option above.

How Fast Should You Lose Weight?

Most nutrition experts recommend losing no more than 1–2 pounds per week. Faster loss increases the risk of muscle loss, nutritional deficiencies, and metabolic adaptation (where your body slows down to conserve energy). A modest deficit of 250–500 calories per day is sustainable for most people over months of consistent eating.

Macronutrients Within Your Calorie Budget

Once you know your calorie target, the next step is distributing those calories across protein, carbohydrates, and fat. A high-protein diet (0.7–1 g of protein per pound of body weight) is particularly effective at preserving muscle while in a deficit. Use the Macronutrient Calculator to split your calorie budget into grams of each macronutrient.

Frequently Asked Questions

What is the minimum safe calorie intake?

General guidelines suggest 1,200 calories per day for women and 1,500 calories per day for men as minimums for most adults. Going below these levels without medical supervision risks nutrient deficiencies, fatigue, and loss of muscle mass. If your calculated target falls below these thresholds, choose a smaller weekly loss rate or consult a registered dietitian.

Why am I not losing weight even in a deficit?

Several factors can stall progress: inaccurate calorie tracking (underestimating food intake is common), metabolic adaptation after extended dieting, water retention from stress or high sodium, or miscalculated TDEE. Consider recalculating your TDEE and tracking calories more precisely for a few weeks.

Does eating less always mean losing fat?

A true calorie deficit will always result in weight loss over time, but the composition (fat vs. muscle) matters. Adequate protein intake, resistance training, and a moderate (not extreme) deficit help ensure the weight you lose comes primarily from fat rather than muscle.

Should I eat back calories I burn exercising?

This depends on how you selected your activity multiplier. If you chose an activity level that accurately reflects your exercise, your TDEE already includes those burned calories — you don't need to eat them back. If you chose "sedentary" and are newly adding exercise, eating back 50–75% of estimated exercise calories is a reasonable middle ground.

How is this different from a TDEE calculator?

A TDEE calculator tells you how many calories to eat to maintain your current weight. This calorie deficit calculator takes that number and subtracts a deficit to give you a weight-loss target. Think of TDEE as the starting point and calorie deficit as the adjustment.