Calorie deficit calculator: when will you reach your goal?

A calorie deficit means eating less energy than your body uses, so it makes up the difference from its reserves, mostly body fat. The calculator first works out your daily energy needs (TDEE) with your chosen formula and activity level, just like the calorie calculator.

You set your weekly pace as a percentage of body weight, because losing 2 lb a week means something very different at 260 lb than at 130 lb. Weekly target = pace × current weight, and daily deficit = weekly change × 7,700 calories per kg ÷ 7 (about 3,500 per pound).

The plan recalculates every week. As your weight drops, so do your BMR and TDEE, so your daily calorie target edges down week by week. That's why weight loss slows toward the end, and why this is more accurate than a flat "minus 500 calories" rule. The NIDDK Body Weight Planner uses the same dynamic idea.

Weekly pace	At 176 lb (80 kg)	Best for
0.25%	about 0.4 lb a week	a few pounds to lose, or while building muscle
0.5%	about 0.9 lb a week	sustainable for most people
0.75%	about 1.3 lb a week	more to lose, with good tracking
1%	about 1.8 lb a week	short periods, larger amounts to lose

The CDC calls 1 to 2 pounds a week gradual and steady, and most guidelines recommend 0.5 to 1% of body weight a week. Faster than 1% raises the risk of muscle loss, gallstones and regaining weight, so the calculator won't build a faster plan.

The calculator never suggests eating less than:

• 1,200 calories a day for women or 1,500 for men, and
• your own BMR, if that's higher.

If your chosen pace would need fewer calories than that, intake stays at the minimum, weight loss slows and your goal date moves later. The plan marks those weeks. Very low calorie diets below these levels should only be done under medical supervision.

We don't make a plan:

• under 18, because growing bodies need energy; if you're worried, talk to a pediatrician, and the BMI calculator for kids is a good first look
• during pregnancy or while breastfeeding, because a calorie deficit isn't recommended then without medical supervision

If your goal weight would mean a BMI under 18.5, you'll see a warning.

A 35-year-old woman, 5 ft 5 in (165 cm), 176 lb (80 kg), lightly active, wants to reach 159 lb (72 kg). Her Mifflin TDEE is about 2,318 calories, and her safe minimum is her BMR, about 1,495 calories.

Pace	Daily intake at the start	Time to goal
0.25%	about 2,100 cal	about 42 weeks
0.5%	about 1,880 cal	about 21 weeks
0.75%	about 1,660 cal	about 14 weeks
1%	1,495 cal (at the minimum)	about 11 weeks

At 1% she'd need about 1,440 calories at the start, which is below her BMR, so intake stays at 1,495. At 0.5%, about 1,880 calories gets her there in five months and is far easier to stick with.

If you want to reach your goal by a certain event, like a wedding, a trip or a race, choose plan by goal date. The calculator works out the weekly pace and daily intake you'd need and tells you whether it's:

• doable, if the pace is 1% a week or less and intake stays above the safe minimum
• too fast, if either condition fails. Then choose a later date or a smaller goal.

In the example above, reaching the goal in 87 days (about 12 weeks) would take a pace of about 0.84% a week and about 1,575 calories a day, which is still doable. In 178 days it would take 0.41% a week and about 1,955 calories.

For a gain plan (goal above current weight), the same logic works with a surplus.

The plan is a model, and real life will differ:

• In the first week or two you often lose more, because water leaves with stored carbs. Later it slows.
• Your weight can swing 2 to 4 lb a day with water and digestion. Watch the weekly average, not single weigh-ins.
• 7,700 calories per kg is an average: some of what you lose is muscle and water, so the real energy content varies.
• After 2 to 4 weeks, use refine mode in the calorie calculator to find your real TDEE from what you ate and how your weight changed, and update the plan.

To keep muscle while losing weight, check your protein needs and keep up strength training. If you have diabetes, an eating disorder or take medication that affects weight, talk to your doctor or a registered dietitian before you start.