Calorie Deficit Calculator With Goal Date

Estimates only. Talk to a doctor or registered dietitian before acting on these numbers for medical reasons.

How the calculator works

It runs the same steps as the Deficit app when it sets up a cut, with the same numbers.

1. Lean mass. Your weight minus your fat: 176 lb at 20% body fat is about 141 lb of lean mass.
2. Resting burn. The Cunningham equation, from a 1991 review of resting metabolism studies: 370 + 21.6 × lean mass in kg. Lean mass explains most of the difference in resting burn between adults, so this is where the calculator starts.
3. Daily burn. Resting burn × an activity level from your steps and workouts (1.2 to 1.55) × a digestion factor from how you eat (1.08 to 1.15). This is your maintenance number.
4. Sports days. A 1-hour run, ride, swim or tennis session burns more than the activity level holds, so on those days you eat more. The calculator counts one hour at a moderate effort, the average of running, cycling, swimming and tennis in the 2024 Compendium of Physical Activities, above what you burn at rest. About 520 calories at 176 lb. The forecast assumes you eat it back on the day, as the app does with Fuel.
5. Deficit. A percentage below maintenance, set by your body fat. The slider lets you go gentler or faster.
6. Weekly loss and date. Daily deficit × 7 ÷ 7,700 calories per kg of fat (about 3,500 per lb). The plan runs at that rate until it reaches your goal.

Maintenance = (370 + 21.6 × lean kg) × activity × digestion

An example: a 176 lb man at 20% body fat who walks 5,000 to 8,000 steps and lifts once or twice a week. His maintenance is 2,456 calories a day. At the suggested pace he eats 1,904 calories and 132 g of protein a day, and loses about 1.1 lb a week. Your own maintenance is on the TDEE calculator.

How long will it take to reach your goal weight?

For the same man, this is how many weeks it takes to lose 10, 20 or 30 lb at three paces:

Anything over 12 weeks takes more than one cut, with a break at maintenance between them. A faster pace saves weeks but costs more hunger and more risk to muscle, so the calculator suggests a pace from your body fat.

How big should your deficit be?

The suggested deficit grows with body fat. A lean person who cuts hard loses more muscle, so the calculator starts them gentler:

"Deficit" is how far below maintenance you eat: at 20%, a person who burns 2,500 calories a day eats 2,000. Between these points the calculator draws a straight line, so a man at 20% body fat gets 22.5%.

The pace label reads your weekly loss as a share of body weight. Under 0.45% a week is conservative, under 0.65% moderate, up to 1% optimal, and above 1% aggressive. A review of contest preparation in natural bodybuilders suggests 0.5 to 1% a week to keep muscle.

How accurate is the goal date?

Scale weight moves a few pounds from day to day with water, salt and food in your gut. That is why the chart shows typical weigh-ins around the plan line: a bad week on the scale does not mean the plan failed.

It is a best case. The 7,700-calorie rule also gets less accurate the longer you diet: as you lose weight you burn less, partly because a smaller body costs less to move and partly through adaptation, so the real loss slows. The app handles this by checking your trend weight every week and moving your target. It also caps one cut at 12 weeks. If your goal needs more, the calculator shows where you will be after 12 weeks. After that you take a break at maintenance and set a new plan.