Calorie deficit calculator

A calorie deficit happens when you take in fewer calories than your body uses over time. Because stored energy has to make up the difference, a sustained deficit is what drives fat loss. This tool estimates your maintenance calories — your total daily energy expenditure, or TDEE — using the Mifflin-St Jeor equation and an activity factor, then subtracts a daily deficit to suggest a target intake.

Roughly 3,500 calories is often used as a rule-of-thumb estimate for a pound of body fat, so a 500-calorie daily deficit is commonly associated with about 1 pound of loss per week, and a 1,000-calorie deficit with about 2 pounds. These are population-level estimates — your real results depend on many factors and can vary week to week.

For most adults, a moderate deficit of roughly 300 to 1,000 calories per day — supporting about 1 to 2 pounds of weight loss per week — is a commonly cited range for gradual, sustainable loss. Slower can be easier to maintain, protect more muscle, and feel less punishing.

This calculator will also flag when a target dips below a general daily-intake floor (around 1,200 calories for women and 1,500 for men). Eating below that without professional supervision may make it hard to get enough nutrients. When a target looks too low, easing to a 1 lb/week pace or speaking with a provider is usually the better move.

A deficit that's too large can backfire. Common warning signs include persistent fatigue or dizziness, constant hunger and preoccupation with food, poor sleep, mood changes, hair thinning, feeling cold, workouts that suddenly feel much harder, or menstrual changes.

If you notice several of these, it may help to raise your intake toward maintenance for a while and reassess. Rapid loss also tends to come with more muscle loss and is often harder to keep off than a slower, steadier approach. Anyone with a medical condition, who is pregnant or breastfeeding, or with a history of disordered eating should talk with a licensed provider before starting a deficit.

You can build a deficit by eating a bit less, moving a bit more, or both. A few habits tend to make it more sustainable: prioritize protein to help preserve muscle and stay full, load up on fiber-rich vegetables, fruit, and whole grains, drink enough water, protect your sleep, and add regular activity — including some resistance training.

Some people also benefit from provider-guided care. FitRx pairs you with licensed U.S. providers who can review your health history and, when appropriate, build a personalized plan that may include lifestyle coaching or prescription options such as GLP-1 medications. Whether treatment is right for you is a decision only a licensed provider can make — this tool doesn't prescribe anything or guarantee results.