TDEE Based · Safe Deficit · Weight Loss Timeline

Calorie Deficit Calculator

Calculate your daily calorie target for weight loss. Enter your stats to find your TDEE, then choose a safe deficit to lose 0.5 to 2 lbs per week with a realistic timeline.

Last updated · Calorie floor guidance checked against the AHA/ACC/TOS guideline and NIDDK

TDEE-Based Calorie Target
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Calorie Deficit Calculator
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Enter your details to calculate your daily calorie target for weight loss.

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How Calorie Deficit Works

To lose about 1 pound a week, eat roughly 500 calories a day below your maintenance calories (TDEE), since 3,500 calories is the traditional estimate for a pound of body fat. The calculator estimates your TDEE with the Mifflin-St Jeor equation, subtracts the deficit for your weekly goal, and never sets a target below 1,200 calories for women or 1,500 for men.

A calorie deficit means consuming fewer calories than your body burns (TDEE). Since 1 lb of fat is approximately 3,500 calories, a 500 calorie/day deficit creates roughly 1 lb/week of fat loss. This is the basis for most weight loss recommendations.

Your TDEE (Total Daily Energy Expenditure) is calculated from your BMR (Basal Metabolic Rate: calories burned at rest) multiplied by an activity factor. This calculator uses the Mifflin-St Jeor equation, considered the most accurate for most people. Never go below 1,200 calories (women) or 1,500 calories (men) without medical supervision.

Mifflin-St Jeor Equation

The most validated BMR formula for most adults. Men: BMR = 10 x weight(kg) + 6.25 x height(cm) - 5 x age + 5. Women: BMR = 10 x weight(kg) + 6.25 x height(cm) - 5 x age - 161. Multiply by activity factor (1.2-1.9) to get TDEE. Accuracy within 10% for 70-80% of people; less accurate for extremes of body composition.

Safe Rate of Loss

Most health authorities recommend losing no more than 0.5-1 kg (1-2 lbs) per week. Faster loss increases lean muscle loss, nutrient deficiencies, and metabolic adaptation. A 500 cal/day deficit (1 lb/week) is the classic evidence-based target. Deficits beyond 1,000 cal/day are generally not recommended without medical supervision.

Protein During Deficit

Higher protein intake (1.6-2.2g per kg of body weight) during a calorie deficit preserves lean muscle mass. Protein also has the highest thermic effect of food (20-30% of calories are used in digestion vs 5-10% for carbs and 0-3% for fat). Prioritising protein at each meal is one of the most effective practical strategies for maintaining muscle while losing fat.

Metabolic Adaptation

As you lose weight, your TDEE decreases because: smaller body requires less energy, metabolic rate adapts (adaptive thermogenesis). This is why weight loss slows over time even at the same deficit. Plan to recalculate TDEE after every 5-10 lbs of weight loss and adjust calories downward or increase activity to maintain the deficit.

Daily Calorie Targets by Weekly Goal

Two lightly active examples (activity factor 1.375), worked out with the same formula the calculator uses: a 35-year-old woman, 5'5" and 170 lb, with a TDEE of 2,017 calories, and a 40-year-old man, 5'10" and 200 lb, with a TDEE of 2,507.

Weekly goalDaily deficitWoman, 170 lbMan, 200 lb
0.5 lb (0.23 kg)250 kcal1,767 kcal2,257 kcal
1 lb (0.45 kg)500 kcal1,517 kcal2,007 kcal
1.5 lb (0.68 kg)750 kcal1,267 kcal1,757 kcal
2 lb (0.91 kg)1,000 kcal1,200 kcal (floor)1,507 kcal

At 2 lb a week the woman's target would fall to 1,017 calories, so the calculator holds it at 1,200. Her real deficit becomes 817 calories and the expected loss about 1.6 lb a week. If the floor kicks in for you, a slower goal is the better choice.

How Long It Takes, and Why the 3,500 Rule Overshoots

The simple rule divides the weight you want to lose by your weekly loss. This table shows weeks needed at a steady deficit:

Daily deficit10 lb20 lb30 lb50 lb
250 kcal20 weeks40 weeks60 weeks100 weeks
500 kcal10 weeks20 weeks30 weeks50 weeks
750 kcal6.7 weeks13.3 weeks20 weeks33.3 weeks
1,000 kcal5 weeks10 weeks15 weeks25 weeks

Real results are faster at first and slower later. The first week or two often shows a bigger drop from water and stored glycogen. After that, a smaller body burns fewer calories, so the same intake gives a shrinking deficit.

NIH researcher Kevin Hall's model, which powers the NIDDK Body Weight Planner, gives a better long-run rule of thumb: each 10 calories a day you cut lowers your eventual weight by about 1 lb, with roughly half of that change in the first year. Cutting 500 calories a day would suggest 52 lb in a year by the 3,500 rule, but closer to 25 lb by the dynamic model. That is why recalculating every 10 lb or so matters.

Calorie Floors and a Safe Pace

The calculator will not go below 1,200 calories for women or 1,500 for men. US adult obesity guidelines (AHA/ACC/TOS, 2013) describe weight loss diets of 1,200 to 1,500 calories a day for women and 1,500 to 1,800 for men, or a daily deficit of 500 to 750 calories. Diets under 800 calories a day are very low calorie diets and are used only with medical supervision.

The CDC notes that people who lose weight gradually, about 1 to 2 lb a week, are more likely to keep it off. Common mistakes that stall progress:

  • Choosing a higher activity level than you really have. A desk job plus three workouts a week is usually "lightly active".
  • Counting workouts twice: the activity factor already includes your usual exercise.
  • Never updating the numbers. A 20 lb loss lowers TDEE by roughly 100 to 150 calories for most adults, so the old target stops working.

Numbers here are estimates. If you are pregnant or breastfeeding, under 18, take medication for diabetes, or have a history of disordered eating, plan any deficit with your doctor or a registered dietitian. For macros at your target, see the macro calculator; for maintenance calories by activity level, the calorie calculator.

Method and sources. BMR uses the Mifflin-St Jeor equation (1990): 10 × weight in kg + 6.25 × height in cm − 5 × age, then +5 for men or −161 for women. TDEE = BMR × activity factor (1.2 to 1.9). Daily deficit = weekly goal in lb × 3,500 ÷ 7. Every table value was computed with those formulas. Long-run weight change: Hall et al., The Lancet 2011, and the NIDDK Body Weight Planner. Calorie ranges: 2013 AHA/ACC/TOS Guideline for the Management of Overweight and Obesity in Adults. Pace of loss: CDC. Estimates only, not medical advice.
Calorie calculations are estimates. Individual metabolism varies. Consult a healthcare professional or registered dietitian before starting any weight loss program, especially if you have medical conditions.

Frequently Asked Questions

A calorie deficit occurs when you consume fewer calories than your body burns in a day. Your body then uses stored fat (and some protein from muscle) to make up the difference. A 500 calorie/day deficit creates a weekly deficit of 3,500 calories, roughly equivalent to 1 lb (0.45 kg) of fat. This is why 1 lb/week is the standard recommended rate of loss.

Start from your TDEE (Total Daily Energy Expenditure) and subtract your target deficit. This calculator calculates your TDEE using the Mifflin-St Jeor equation and your activity level. A 500 cal/day deficit is recommended for most people aiming for 1 lb/week loss. Never go below 1,200 calories (women) or 1,500 calories (men) without medical supervision.

The traditional estimate is 3,500 calories = 1 lb of fat. This comes from the energy content of adipose tissue (~7,700 kcal/kg). In practice, weight loss is not perfectly linear because the body also loses water, glycogen, and some muscle: and metabolic rate adapts. The 3,500 calorie rule is a useful approximation; actual results vary by individual.

TDEE (Total Daily Energy Expenditure) is the total calories your body burns in a day, accounting for all activity. It's calculated as BMR x activity factor. BMR is the calories needed at rest to maintain basic functions. Sedentary TDEE: BMR x 1.2. Moderately active: BMR x 1.55. Very active: BMR x 1.725. For most adults, TDEE ranges from 1,600 to 3,000 calories depending on size and activity.

Safe rate: 0.5-1 kg (1-2 lbs) per week for most adults. For people with obesity (BMI 35+), 2-2.5 lbs/week may be appropriate under medical supervision. Faster loss: increases muscle loss, micronutrient deficiencies, gallstones, and metabolic adaptation. Very low calorie diets (under 800 kcal) require medical supervision. Studies consistently show slower loss rates result in more sustainable outcomes and better muscle preservation.

BMR (Basal Metabolic Rate) is the calories your body burns at complete rest: just to maintain basic functions like breathing, circulation, and organ function. It accounts for 60-70% of total daily calorie burn. The Mifflin-St Jeor equation: Men: (10 x weight_kg) + (6.25 x height_cm) - (5 x age) + 5. Women: (10 x weight_kg) + (6.25 x height_cm) - (5 x age) - 161.

This depends on how your TDEE was calculated. If using an activity multiplier (like this calculator), exercise is already partially included. If tracking individual workouts separately, eating back 50-75% of exercise calories is a conservative approach (trackers often overestimate). The simplest approach: choose an accurate activity multiplier and maintain a consistent deficit from that TDEE without separately tracking workout calories.

Plateaus occur because: you've lost weight (lower TDEE), metabolic adaptation, or tracking errors accumulate. Solutions: recalculate TDEE and reduce calories by 100-150 kcal, increase activity rather than further reducing food, take a 1-2 week 'diet break' at maintenance calories (some research suggests this limits adaptive thermogenesis), recheck food logging accuracy (portion creep is common). Most plateaus are not biological failures but tracking or calculation issues.

For weight loss, calories are the primary driver: but food type matters for satiety, muscle preservation, and adherence. High-protein foods preserve muscle during deficit. High-fiber foods increase satiety per calorie. Ultra-processed foods are engineered to be hyperpalatable and lead to overconsumption. Practical hierarchy: first get calories right, then prioritise protein (1.6-2g/kg), then vegetables and fiber, then overall diet quality.

US obesity guidelines (AHA/ACC/TOS, 2013) describe weight loss diets of 1,200 to 1,500 kcal a day for women and 1,500 to 1,800 for men, and this calculator will not go below 1,200 or 1,500. Very low calorie diets (VLCDs, 400-800 kcal/day) are medically supervised programs for specific conditions. Going below minimums risks: nutrient deficiencies, muscle loss, hair loss, hormonal disruption, gallstones, and disordered eating. If your calculated target is below the minimum, reduce your deficit goal or extend your timeline.

By the 3,500 calorie rule, about 20 weeks at a 500 calorie daily deficit (1 lb a week), or 10 weeks at 1,000 a day if that target stays above your calorie floor. Expect the pace to slow after the first month, because your maintenance calories drop as you lose weight. Recalculate every 10 lb to keep the deficit real.

For many women, 1,200 calories is the lowest intake commonly used for weight loss without medical supervision; for most men the lower bound is about 1,500. A tall or very active person may lose weight too fast and feel unwell at that level, so it is not a target for everyone. Diets below 800 calories a day are only used under a doctor's care.
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