How big a calorie deficit do I need to lose 1 lb per week?

A 500 calorie daily deficit produces roughly 1 lb of weight loss per week (3,500 calories ≈ 1 lb of fat). For 2 lb per week, aim for a 1,000 calorie daily deficit, though this is aggressive and often hard to sustain. Most adults do best at 300-500 calories below maintenance: slow enough to preserve muscle but fast enough to stay motivated.

Should I cut more calories or exercise more?

Both work, but diet does most of the heavy lifting. Eating 500 calories less per day requires skipping one meal or downsizing portions. Burning 500 extra calories per day requires roughly 45-60 minutes of moderate cardio. Combining a smaller diet cut (300 cal) with modest exercise (200 cal burned) is more sustainable than either extreme alone.

Is my weight loss going to slow down even if I keep my deficit?

Yes - this is metabolic adaptation. As you lose weight, your BMR drops because there is less body mass to maintain, and adaptive thermogenesis further reduces non-exercise activity. A 500 cal deficit at 200 lbs may slow to a 350 cal effective deficit at 175 lbs. Recalculate your TDEE every 10-15 lbs lost to stay on track.

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Calorie Deficit Calculator (Diet)

Calculate your daily calorie target for weight loss. Includes weekly weight loss projections.

HEALTH

The Calorie Deficit Calculator helps you determine your daily calorie target for weight loss.

Based on BMR (Mifflin-St Jeor) and TDEE. Choose a weight loss rate from 0.25 to 1 kg per week. Includes a weekly weight loss projection and safe minimum limits.

Disclaimer: For certain medical conditions, consult a doctor or nutritionist.

Calorie Deficit & Weight Loss Calculator

Calculate daily calorie needs, required deficit, and estimated diet duration based on your body data. Uses the Mifflin-St Jeor formula recommended for modern populations.

Healthy Calorie Deficit Guide

What is a calorie deficit?

A calorie deficit occurs when you consume fewer calories than your body burns (TDEE). One kilogram of body fat equals approximately 7,700 kcal. To lose 0.5 kg per week, you need a deficit of about 550 kcal per day.

Why is 0.5–1 kg/week the ideal range?

Loss in this range has been proven to better preserve muscle mass, maintain daily energy, and is easier to sustain long-term. Losing fat too quickly (>1 kg/week) risks nutritional deficiency, muscle loss, and metabolic slowdown.

Dangers of yo-yo dieting

Overly aggressive strict diets often end with rebound — weight returns and even exceeds the starting weight. This happens because the body lowers its metabolic rate in response to extreme calorie restriction. A gradual and consistent approach is far more effective long-term.

Minimum safe intake

WHO and dietitians recommend daily calorie intake of no less than 1,200 kcal for women and 1,500 kcal for men. Below these numbers, the risk of vitamin and mineral deficiency and muscle loss increases significantly.

Mifflin-St Jeor Formula

Male:    BMR = 10×BW + 6.25×H − 5×Age + 5
Female:  BMR = 10×BW + 6.25×H − 5×Age − 161
BW = body weight (kg) · H = height (cm) · Age = years
TDEE = BMR × activity factor · Deficit = speed (kg/wk) × 7,700 ÷ 7

Practical tips for maintaining deficit

Prioritize protein (1.6–2.2 g/kg BW) to maintain muscle mass during diet.
Add vegetables and fiber to stay fuller longer without adding many calories.
Track food intake at least at the start of the program to build awareness.
Do strength training at least 2–3×/week to prevent muscle loss.
Weigh yourself in the morning on an empty stomach, and average 7 days to see accurate trends.
If stuck for >2 weeks, reassess TDEE — activity or intake may have shifted.

Disclaimer: This calculator provides estimates and does not replace professional medical advice. Each individual has different metabolic responses. Consult your diet plan with a doctor or nutritionist before starting a weight loss program, especially if you have certain medical conditions such as diabetes, thyroid disorders, or a history of eating disorders.

Calculator information

How to use this calculator

Enter your sex, age (years), height (cm), and current weight (kg).
Select an activity level: sedentary, light (exercise 1-3x/week), moderate (3-5x), active (6-7x), or very active (athlete or heavy labor).
Choose a target rate of loss: 0.25 kg/week (mild deficit), 0.5 kg/week (moderate), 0.75 kg/week (aggressive), or 1 kg/week (maximum safe).
Click Calculate to see BMR (resting calories), TDEE (total daily energy expenditure), and your deficit target.
Review projected weight loss at 4, 8, and 12 weeks and the safe minimum intake (1,200 kcal for women, 1,500 kcal for men).
Track daily intake in an app such as MyFitnessPal or Cronometer. Tip: combine the deficit with resistance training to preserve lean mass.

Mifflin-St Jeor BMR and TDEE

BMR Male = 10*W + 6.25*H - 5*Age + 5; BMR Female = 10*W + 6.25*H - 5*Age - 161; TDEE = BMR * Activity Factor; Target Calories = TDEE - Deficit (1 kg fat ~7,700 kcal)

W = body weight (kg)
H = height (cm)
Age in years
Activity factor: 1.2 (sedentary), 1.375 (light), 1.55 (moderate), 1.725 (active), 1.9 (very active)
0.5 kg/week deficit equals about 550 kcal/day

Mifflin-St Jeor (1990) is 5-10% more accurate than the older Harris-Benedict equation.

Worked example: 30-year-old woman, 165 cm, 70 kg, light activity, target 0.5 kg/week

Given:

Sex = female
Age = 30, height = 165 cm, weight = 70 kg
Activity factor = 1.375
Deficit target = 550 kcal/day (0.5 kg/week)

Steps:

BMR = 10*70 + 6.25*165 - 5*30 - 161 = 700 + 1,031.25 - 150 - 161 = 1,420.25 kcal
TDEE = 1,420.25 * 1.375 = 1,953 kcal
Target intake = 1,953 - 550 = 1,403 kcal/day
12-week projection: 0.5 kg * 12 = 6 kg

Result: Eat about 1,403 kcal/day (still above the 1,200 kcal floor for women). Expected loss is about 6 kg over 12 weeks, ending at 64 kg.

Frequently asked questions

What is the minimum safe daily calorie intake?

The American College of Sports Medicine and the U.S. Dietary Guidelines recommend a floor of about 1,200 kcal/day for women and 1,500 kcal/day for men when dieting. Going lower risks micronutrient deficits, metabolic adaptation, and lean-mass loss. Very-low-calorie diets (VLCDs) under 800 kcal should only be done under medical supervision.

Is 1 kg of body fat really 7,700 calories?

The 7,700 kcal/kg figure (about 3,500 kcal/lb) is a classic approximation. Modern research (Hall et al., 2011) shows it oversimplifies, because it ignores metabolic adaptation. Weight loss tends to slow over time as BMR falls with body weight, so periodic recalculation is needed.

How do I break through a diet plateau?

Plateaus typically appear after 8-12 weeks due to metabolic adaptation. Tactics: (1) 1-2 refeed days per week at maintenance, (2) a 1-2 week diet break at TDEE after 12-16 weeks of deficit, (3) recalculate TDEE after each 5% drop in body weight, (4) vary training stimulus, (5) sleep 7-9 hours, since poor sleep raises ghrelin (the hunger hormone).

What role does protein play during a calorie deficit?

Higher protein intake (1.6-2.2 g/kg body weight) while cutting helps preserve lean mass, improves satiety, and has a high thermic effect (about 25% of protein calories are burned during digestion). Aragon & Schoenfeld (2013) found that high-protein diets combined with resistance training produce 2-3x more fat loss with better muscle retention than low-protein dieting.

Is a calorie deficit appropriate for everyone?

No. A calorie deficit is not recommended for: pregnant or nursing women, growing children and teens, frail adults over 70 without supervision, anyone with an eating disorder (anorexia, bulimia), people with type 1 diabetes without physician input, or anyone with a BMI under 18.5. Consult a registered dietitian (RD/RDN) or your physician before starting a strict diet.

Sources & references

Mifflin et al. 1990 - A new predictive equation for resting energy expenditure — American Journal of Clinical Nutrition (PubMed/NIH)
Dietary Reference Intakes - Energy — U.S. Department of Agriculture / NIH
Dietary Guidelines for Americans 2020-2025 — U.S. Department of Health and Human Services / USDA

Last updated: May 11, 2026

Calorie Deficit Calculator (Diet)

Calorie Deficit & Weight Loss Calculator

Healthy Calorie Deficit Guide

Calculator information

📋 How to use this calculator

🧮 Mifflin-St Jeor BMR and TDEE

💡 Worked example: 30-year-old woman, 165 cm, 70 kg, light activity, target 0.5 kg/week

❓ Frequently asked questions

📚 Sources & references

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How to use this calculator

Mifflin-St Jeor BMR and TDEE

Worked example: 30-year-old woman, 165 cm, 70 kg, light activity, target 0.5 kg/week

Frequently asked questions

Sources & references