Calorie Deficit Calculator
Enter your body details, a goal weight and a weekly loss rate or number of weeks to estimate maintenance calories, your daily target, the deficit and time to goal.
Last updated November 3, 2026
Must be below current weight
Result
About 1,595 kcal a day
A deficit of 500 kcal a day (24% below maintenance) to lose 20 lb in about 20 weeks.
| Maintenance calories (TDEE) | 2,095 kcal |
|---|---|
| Daily calorie target | 1,595 kcal |
| Daily deficit | 500 kcal (23.9% of maintenance) |
| Weekly loss | 1 lb (0.59% of body weight) |
| Time to goal | 20 weeks |
No safety flags at this pace: the target is above 1,200 kcal, the loss is under 1% of body weight a week and the deficit is under 25% of maintenance.
The 3,500 kcal per lb (7,700 per kg) rule is a rule of thumb. It overstates long-term loss because metabolism adapts, so expect to adjust. General estimate, not medical advice.
Show the work
Formula: target = TDEE − deficit; TDEE = BMR × activity factor; deficit = weekly loss × 3,500 kcal per lb ÷ 7
- You entered 5 ft 7 in, 170 lb, goal 150 lb. The formulas use 170.2 cm, 77.1 kg and a goal of 68 kg.
- BMR = 10 × 77.1 + 6.25 × 170.2 − 5 × 30 − 161 = 1,523.7 kcal.
- Maintenance = 1,523.7 × 1.375 = 2,095 kcal.
- Weight to lose = 170 lb − 150 lb = 20 lb.
- Time = 20 lb ÷ 1 lb a week = 20 weeks.
- Deficit = 1 lb × 3,500 ÷ 7 = 500 kcal a day (7,716 kcal per kg).
- Target = 2,095 kcal − 500 kcal = 1,595 kcal.
- Checks: minimum 1,200 kcal, loss 0.59% of body weight a week (limit 1%), deficit 23.9% of maintenance (limit 25%).
Result: About 1,595 kcal a day, a 500 kcal deficit, about 20 weeks to goal
How the daily deficit is calculated
TDEE = BMR × activity factor
deficit per day = lb per week × 3,500 ÷ 7
target = TDEE − deficit
Maintenance calories come from the same method as the Calorie Calculator: the Mifflin-St Jeor equation gives basal metabolic rate (BMR), and an activity factor from 1.2 to 1.9 turns it into total daily energy expenditure (TDEE).
Losing 1 lb a week at 3,500 kcal per lb needs 3,500 ÷ 7 = 500 kcal a day below maintenance. With a goal date, the calculator divides the pounds to lose by the weeks to get the weekly rate, then applies the same step. The goal weight must be below your current weight.
See how we calculate for the formulas, sources and review schedule behind every calculator.
Also useful alongside this calculator: Percentage Calculator, Date Calculator and BMI Calculator.
This is an estimate, not medical advice
This calculator gives a general estimate from the published methods listed under Sources. It does not diagnose anything or replace advice from a doctor, dietitian or other qualified health professional, and individual needs differ. This page has not been reviewed by a medical professional.
Choosing a deficit size and pace
In the example below, 0.5 lb a week costs 250 kcal a day, about 12% of maintenance, while 1 lb a week costs 500 kcal, about 24%. Then it climbs: 1.5 lb a week is 750 kcal (36%) and 2 lb a week is 1,000 kcal (48%).
If you set a goal date, check the weekly loss first. Reaching 150 lb in 12 weeks means about 1.67 lb a week and a target of 1,262 kcal, a deficit near 40% of maintenance. Moving the date out to 20 weeks brings it down to 500 kcal.
Safety limits and when to ask a clinician
The calculator flags four cautions instead of hiding them: a target under 1,200 kcal for women or 1,500 kcal for men, the amounts commonly cited as the lowest intakes without medical supervision; loss faster than about 1% of body weight per week, roughly 1.7 lb at 170 lb; a deficit over about 25% of maintenance; and a goal weight with a BMI under 18.5.
These thresholds are common guidance, not a diagnosis, and no checked primary source backs them, as the source notes say. A flag means talk to a doctor or dietitian before you start. Do so first if you are pregnant, under 18, have diabetes, disordered eating or a heart or kidney condition.
Why the 3,500 calorie rule is approximate
The figure of 3,500 kcal per pound, about 7,700 per kg, is a rule of thumb that treats weight loss as a straight line. As you get lighter your maintenance calories fall, and metabolism can adapt, so the same deficit removes less weight in month four than in month one. The Hall et al. paper under Sources describes body weight responding slowly to intake. Weigh weekly and recalculate every few weeks.
Protein, activity and the rest of your plan
Use the Protein Calculator to set a daily protein range, and the Macro Calculator to split your target into grams. At 1,595 kcal, a balanced 30/30/40 split gives about 120 g of protein, 53 g of fat and 160 g of carbohydrate.
Pick the activity level that matches a typical week, because overstating it inflates the target.
Sources
Official and primary sources for the statements on this page. Their authors have not reviewed or endorsed this page.
- Mifflin MD, St Jeor ST, Hill LA, Scott BJ, Daugherty SA, Koh YO. A new predictive equation for resting energy expenditure in healthy individuals. Am J Clin Nutr 1990;51(2):241-247. Source of the Mifflin-St Jeor equation used for the basal rate: 10 × weight (kg) + 6.25 × height (cm) − 5 × age, plus 5 for men or minus 161 for women
- Hall KD, Sacks G, Chandramohan D, et al. Quantification of the effect of energy imbalance on bodyweight. Lancet 2011;378(9793):826-837. Context only: body weight responds slowly to a change in intake, so a fixed 3,500 calories per pound overstates long-term loss and the dates on this page are rough guides, not predictions
We did not find a checked primary source for the activity multipliers (1.2 to 1.9) or for the figure of about 3,500 calories per pound. They are common rules of thumb, and the Hall paper above does not state the 3,500 figure.
We also did not find a checked primary source for the 1,200 and 1,500 kcal minimums, the 1% of body weight per week limit or the 25% deficit limit. They are commonly cited guidance used here as caution thresholds, not as clinical rules.
How to use the Calorie Deficit Calculator
- Choose units, then enter sex, age, height and current weight.
- Enter a goal weight below your current weight and pick the activity level that fits a typical week.
- Choose how to set the pace: a weekly loss rate, or a target date entered as weeks from today.
- Read your daily calorie target, deficit and time to goal, check for caution notes, then use Copy, Print or Share.
Worked example
A 30-year-old woman who is 5 ft 7 in (170.2 cm) and 170 lb (77.1 kg) wants to reach 150 lb with light activity. Her BMR is 10 × 77.11 + 6.25 × 170.18 − 5 × 30 − 161 = 1,524 kcal, so maintenance is 1,524 × 1.375 = 2,095 kcal. Losing 20 lb at 1 lb a week takes 20 weeks, needs a 500 kcal deficit and gives a target of 1,595 kcal a day.
| Pace | Weeks to goal | Daily deficit | Daily target | Flags |
|---|---|---|---|---|
| 0.5 lb a week | 40 | 250 kcal | 1,845 kcal | None |
| 1 lb a week | 20 | 500 kcal | 1,595 kcal | None |
| 1.5 lb a week | 13.3 | 750 kcal | 1,345 kcal | Deficit over 25% |
| 2 lb a week | 10 | 1,000 kcal | 1,095 kcal | All three cautions |
| Goal in 12 weeks | 12 | 833 kcal | 1,262 kcal | Deficit over 25% |
Frequently asked questions
How many calories should I cut to lose 1 pound a week?
About 500 kcal a day below maintenance, because a pound is commonly estimated at 3,500 kcal and 3,500 ÷ 7 is 500.
What is the lowest calorie target I should eat?
Commonly cited minimums are 1,200 kcal a day for women and 1,500 for men without medical supervision.
Why am I losing weight slower than the calculator says?
The 3,500 kcal rule overstates long-term loss because maintenance falls as you get lighter and metabolism adapts. Recalculate with your current weight.
Are my numbers stored or sent anywhere?
No. The calculation runs in your browser and nothing you enter is saved or uploaded.