Weight Loss Calculator
Estimate your daily calorie needs, calorie deficit, and time to reach your goal weight. Our calculator uses clinically validated formulas including Mifflin-St Jeor, Harris-Benedict, and Katch-McArdle.
Energy Expenditure & Calorie Budget
Daily Caloric Target Breakdown by Goal
Click any objective below to update your primary telemetry dial, 3D orbit, and meal journal.
How the Weight Loss Calculator Works
Our weight loss calculator estimates how many calories you need to eat each day to lose weight at a safe, sustainable rate. It works in three steps:
Calculate Your BMR
Your Basal Metabolic Rate (BMR) is the number of calories your body burns at complete rest. We calculate this using your age, weight, height, and biological sex.
Estimate Your TDEE
Your Total Daily Energy Expenditure (TDEE) is calculated by multiplying your BMR by an activity level multiplier that accounts for your daily movement and exercise habits.
Apply a Calorie Deficit
To lose weight, we subtract 300\u2013500 calories from your TDEE to create a safe calorie deficit. This results in gradual fat loss while preserving muscle mass and energy levels.
How Many Calories Should I Eat to Lose Weight?
The number of calories you should eat to lose weight depends on your individual metabolic rate and activity level. As a general guideline:
Results in approximately 0.5\u20131 lb (0.25\u20130.5 kg) of weight loss per week. Recommended for sustainable, long-term results.
Results in approximately 1\u20132 lbs per week. Higher risk of muscle loss and metabolic adaptation. Should be monitored carefully.
Important: Daily calorie intake should generally not fall below 1,200 kcal for women or 1,500 kcal for men without medical supervision. Use the calculator above to find your personalized daily calorie target.
What Is a Calorie Deficit?
A calorie deficit is the difference between the calories your body burns (your TDEE) and the calories you consume through food and drinks. When you consistently eat fewer calories than you burn, your body draws on stored energy (primarily body fat) to make up the difference, leading to weight loss.
Example: If your TDEE is 2,200 kcal and you eat 1,800 kcal, your deficit is 400 kcal/day
Since approximately 3,500 calories equals 1 pound (0.45 kg) of body fat, a daily deficit of 500 calories theoretically results in about 1 pound of weight loss per week. Learn more in our complete guide to understanding calorie deficits.
BMR vs TDEE: What's the Difference?
Understanding the difference between BMR and TDEE is essential for accurate weight loss planning:
BMR (Basal Metabolic Rate)
The minimum calories your body needs at complete rest to sustain vital functions: breathing, circulation, cell production, and brain activity. BMR typically accounts for 60\u201370% of your total daily calorie burn.
TDEE (Total Daily Energy Expenditure)
Your total calories burned in a day, including BMR + daily movement (NEAT) + exercise (EAT) + digestion (TEF). TDEE is the number you should base your weight loss calorie target on.
How We Calculate Your Daily Calories
Our weight loss calculator supports three peer-reviewed BMR equations. The Mifflin-St Jeor equation is the default, as it is recommended by the Academy of Nutrition and Dietetics.
Mifflin-St Jeor Equation
Formulated in 1990; proven to predict BMR within 10% of indirect calorimetry for healthy adults.
Men: 10W + 6.25H - 5A + 5
Women: 10W + 6.25H - 5A - 161
W = kg, H = cm, A = age in yearsHarris-Benedict Equation
Revised by Roza & Shizgal in 1984; established for broad metabolic clinical assessments.
Men: 88.36 + 13.4W + 4.8H - 5.68A
Women: 447.6 + 9.25W + 3.1H - 4.33A
W = kg, H = cm, A = age in yearsKatch-McArdle Formula
Calculates BMR based strictly on Lean Body Mass (LBM), ideal for lean athletes and bodybuilders.
BMR = 370 + (21.6 \u00d7 LBM)
LBM = Weight \u00d7 (1 - BodyFat%)
LBM = Lean Body Mass in kgExample Weight Loss Calculation
Here is a worked example for a 30-year-old woman who weighs 70 kg (154 lbs), is 165 cm (5\u20195\u2033) tall, and exercises moderately (3\u20134 days per week):
How Long Does It Take to Lose Weight?
The timeline for weight loss depends on the size of your calorie deficit and your starting weight. Here are general estimates based on a consistent daily deficit:
| Daily Deficit | Weekly Loss | Time to Lose 5 kg (11 lbs) | Time to Lose 10 kg (22 lbs) |
|---|---|---|---|
| 250 kcal | ~0.25 kg (0.5 lb) | ~20 weeks | ~40 weeks |
| 500 kcal | ~0.5 kg (1 lb) | ~10 weeks | ~20 weeks |
| 750 kcal | ~0.75 kg (1.5 lbs) | ~7 weeks | ~14 weeks |
| 1,000 kcal | ~1 kg (2.2 lbs) | ~5 weeks | ~10 weeks |
Note: These are estimates. Actual weight loss may be faster initially (due to water weight) and slower over time due to metabolic adaptation. Deficits above 500 kcal/day should be approached cautiously and ideally supervised by a healthcare professional.
Is the Weight Loss Calculator Accurate?
Our calculator uses the Mifflin-St Jeor equation, which research has shown to predict BMR within approximately 10% of measured values for most healthy adults. However, all calorie calculators are estimates because they cannot account for:
- Metabolic adaptation \u2014 your metabolism can slow as you lose weight
- Hormonal variations \u2014 thyroid function, cortisol, and reproductive hormones affect metabolism
- Body composition \u2014 muscle mass burns more calories than fat tissue at rest
- Individual genetics \u2014 metabolic rates vary between people with identical stats
For the most accurate results, use this calculator as a starting point, track your actual weight changes over 2\u20134 weeks, and adjust your calorie target based on real-world results.
Frequently Asked Questions
How many calories should I eat to lose weight?
To lose weight, you need to eat fewer calories than your body burns. A moderate calorie deficit of 300–500 calories below your Total Daily Energy Expenditure (TDEE) is recommended for safe, sustainable weight loss of approximately 0.5–1 lb (0.25–0.5 kg) per week.
What is a calorie deficit?
A calorie deficit occurs when you consume fewer calories than your body expends. For example, if your TDEE is 2,200 calories and you eat 1,800 calories, you have a 400-calorie deficit. Over time, this deficit forces your body to use stored body fat for energy, resulting in weight loss.
What is BMR and how is it different from TDEE?
BMR (Basal Metabolic Rate) is the number of calories your body burns at complete rest to maintain basic life functions like breathing and circulation. TDEE (Total Daily Energy Expenditure) is your BMR plus all additional calories burned through daily activity and exercise. TDEE is the more useful number for weight loss planning.
How is TDEE calculated?
TDEE is calculated by multiplying your BMR by a physical activity multiplier: Sedentary (×1.2), Lightly Active (×1.375), Moderately Active (×1.55), Very Active (×1.725), or Extra Active (×1.9). Our calculator uses the Mifflin-St Jeor equation, which is considered the most accurate BMR formula for most adults.
How long does it take to lose weight?
The rate of weight loss depends on your calorie deficit. A deficit of 500 calories per day results in approximately 1 lb (0.45 kg) of fat loss per week, since 1 lb of body fat contains about 3,500 calories. A 10 lb weight loss would take approximately 10 weeks at this rate.
Can a calorie calculator predict exact weight loss?
No calculator can predict exact weight loss because individual metabolism varies based on genetics, hormones, sleep quality, stress levels, medication, and metabolic adaptation. Our estimates are based on widely accepted clinical formulas and should be used as a starting point, not an absolute guarantee.
What is Zig-Zag Calorie Cycling?
Zig-zag calorie cycling alternates higher-calorie days with lower-calorie deficit days while keeping your total weekly calorie deficit constant. This approach can help prevent metabolic adaptation, reduce diet fatigue, and accommodate social events.
How many calories should I eat per day?
The average daily calorie need is approximately 2,000 kcal for women and 2,500 kcal for men, but this varies significantly based on age, weight, height, and activity level. Use our calculator above to find your personalized daily calorie target for weight loss, maintenance, or muscle gain.