How to use the calorie deficit calculator
Enter your sex, age, height, current weight and activity level. Then set a goal weight and choose a pace: gentle (½ lb a week), steady (1 lb), brisk (1½ lb) or aggressive (2 lb).
You’ll get a daily calorie target, the date you could reach your goal, and a curve showing your projected weight week by week. If your goal would put you under a BMI of 18.5 for your height, the calculator flags it and suggests talking to a clinician first.
How your calorie target is calculated
First the calculator estimates your total daily energy expenditure (TDEE), the same way as our TDEE calculator: resting burn from the Mifflin-St Jeor equation, times your activity factor. Then it subtracts the deficit for your pace.
Daily deficit = pounds per week × 3,500 ÷ 7Target = TDEE − daily deficitTarget never goes below 1,200 (women) or 1,500 (men)So 1 lb a week means a 500-calorie daily deficit, and 2 lb a week means 1,000. The 3,500-calories-per-pound rule is a rough guide, which is why the timeline below doesn’t stop there.
Why the timeline curves instead of running straight
Most calculators divide pounds to lose by pounds per week and call it done. Real bodies don’t work that way. As you get lighter, your body needs less energy, so the same daily intake makes a smaller deficit each week.
Our calculator keeps your intake fixed at your starting target, recalculates your TDEE at your new weight every week, and projects the loss from the deficit that is actually left. If the deficit shrinks to almost nothing, it shows a plateau. That’s your signal that the plan needs to change, not that you failed.
| Pace | Daily target | Straight-line guess | Projected with the curve |
|---|---|---|---|
| ½ lb a week | 1,885 cal | 60 weeks | Plateaus just above goal |
| 1 lb a week | 1,635 cal | 30 weeks | About 38 weeks |
| 1½ lb a week | 1,385 cal | 20 weeks | About 23 weeks |
| 2 lb a week | 1,200 cal (floor) | 15 weeks | About 18 weeks |
Estimates only. The body also adapts in ways no formula captures well, so real progress is often slower. Results vary.
How fast should you lose weight?
The CDC notes that people who lose about 1 to 2 pounds a week are more likely to keep it off. Faster is not better if it costs muscle, energy and sleep, or if you can’t keep it up past week three.
- Gentle or steady suits most people, especially if you have less than 20 pounds to lose, are over 60, or train hard.
- Brisk can work with a lot to lose and good support, with protein kept high.
- Aggressive often hits the calorie floor. Very low intakes make it hard to get enough protein, fiber and nutrients, so they’re best done with medical supervision.
Why the floor? Below about 1,200 calories for women or 1,500 for men, it gets very hard to meet your nutrient needs from food. The calculator won’t plan lower. Very-low-calorie diets should only be done with a clinician.
How to make a deficit work
A calorie target is the plan. These habits make it stick and help the weight come off as fat, not muscle:
- Hit your protein target at every meal. Use the protein calculator.
- Lift weights or do resistance work two to three times a week.
- Fill half your plate with vegetables for fiber and fullness.
- Sleep 7 to 9 hours. In a 2022 trial, adults with overweight who extended their sleep ate about 270 fewer calories a day.
- Drink enough water. Our water intake calculator gives you a daily goal.
- Weigh a few mornings a week and watch the trend, not the day.
Want the meals done for you? The 7-day high-protein meal plan is sized to calorie targets from 1,200 to 2,400, with a grocery list.
When the deficit stops working
If you’ve stuck to your target for three or four weeks and the scale hasn’t moved, one of three things is usually happening. Portions have crept up (it happens to everyone). Your TDEE has fallen as you lost, so recalculate. Or something biological is pushing back: thyroid, insulin resistance, hormones, sleep apnea, medicines or years of yo-yo dieting.
Our why can’t I lose weight quiz helps sort out which is most likely for you.
When a calculator isn’t enough
At GENEVA Primary Care & Med Spa in Alpharetta, our physicians look at what the math can’t: a body-composition scan to track fat and muscle, labs for thyroid, blood sugar and hormones, and a review of your medicines and sleep. Women can get perimenopause and PCOS care through women’s health; men can check testosterone through our men’s health team.
Your plan can include nutrition coaching and, if you qualify, prescription weight loss medicine like GLP-1 medicines, which quiet the hunger signals that make a deficit hard to hold. They are generally for a BMI of 30 or more, or 27 or more with a weight-related condition, and a clinician decides. Check your number with the BMI calculator, or read about medical weight loss at GENEVA. Results vary.
Frequently asked questions
How many calories should I eat to lose weight?
Is 1,200 calories a day enough?
Why am I not losing weight in a calorie deficit?
Is a 1,000-calorie deficit safe?
How long will it take to lose 20 pounds?
Should I count calories or macros?
Does a calorie deficit slow my metabolism?
Sources
- Centers for Disease Control and Prevention. (2025). Steps for losing weight.
- National Institute of Diabetes and Digestive and Kidney Diseases. Body Weight Planner.
- Mifflin, M. D., St Jeor, S. T., et al. (1990). A new predictive equation for resting energy expenditure in healthy individuals. American Journal of Clinical Nutrition, 51(2), 241–247. (Origin of the formula.)
- Tasali, E., et al. (2022). Effect of sleep extension on objectively assessed energy intake among adults with overweight in real-life settings: A randomized clinical trial. JAMA Internal Medicine, 182(4), 365–374.
- Mozaffarian, D., et al. (2025). Nutritional priorities to support GLP-1 therapy for obesity: A joint advisory from the ACLM, ASN, OMA and TOS. Obesity Pillars.
- Rubino, F., et al. (2025). Definition and diagnostic criteria of clinical obesity. The Lancet Diabetes & Endocrinology, 13(3), 221–262.
This tool gives general estimates for healthy adults and is not medical advice, a diagnosis or a treatment plan. It is not meant for anyone pregnant, under 18, or managing a medical condition without their clinician. Talk to a GENEVA provider before making big changes to how you eat, drink or exercise.