Energy-balance explanation checked against the same sourcing used on the nutrition guide.
A calorie deficit means eating less than your Total Daily Energy Expenditure, so your body draws on stored fat to cover the shortfall. That's the entire mechanism behind every weight-loss plan that actually works, regardless of which diet name is stamped on the cover. A 500-calorie daily gap is the usual starting point, since it lands around a pound of loss a week without being brutal to sustain.
Three steps to your own deficit
Step one: find TDEE, the calories your body burns on a normal day with activity included. Step two: decide how large a gap to run. Step three: set daily intake at TDEE minus that gap. The calorie deficit calculator runs all three in about thirty seconds instead of asking you to do the subtraction by hand.
Picking a deficit size
| Deficit size | Daily calories cut | Weekly loss (approx.) |
|---|---|---|
| Mild | 200-300 | 0.3-0.5 lb |
| Moderate (standard) | 500 | ~1 lb |
| Moderate-aggressive | 750 | ~1.5 lb |
| Aggressive | 1,000 | ~2 lb |
Actual loss rate slows as weight drops, since a lighter body burns fewer calories at rest. Anyone with a health condition should get a doctor or registered dietitian to sign off on the target before starting.
Why "1,500 calories" means nothing on its own
For a petite, sedentary woman with a 1,600-calorie TDEE, eating 1,500 is a mild 100-calorie cut. For a tall, active man burning 2,800 calories, 1,500 is a brutal 1,300-calorie gap. The number by itself tells you nothing; it only means something relative to a TDEE you've actually calculated.
What a deficit diet looks like day to day
There's no single "deficit diet." Keto, low-fat, intermittent fasting, counting macros: every one of them works by the same mechanism if it lands you below TDEE, and none of them work if it doesn't. The practical question is which approach you can actually sustain. Higher protein, around 0.7 to 1 gram per pound of body weight, tends to preserve muscle and blunt hunger better than most other levers you could pull. See how much protein per day fits your target.
The 2-pound-a-week math, and why it's rarely the right call
Losing 2 pounds a week means burning roughly 7,000 more calories than you eat over that week, close to a 1,000-calorie daily deficit. That only stays safe if daily intake doesn't drop below about 1,200 to 1,500 calories. Most people with an average TDEE do better, and stick with it longer, running a 500 to 750 calorie deficit instead.
Calculate your deficit
Get a personal TDEE and a target intake for whatever weekly pace you choose.