Mounjaro Calorie Deficit Calculator
Enter your maintenance calories and a target intake (or desired weekly loss) to see the size of your deficit and projected weight change over time.
A calorie deficit is when you eat fewer calories than your body burns. This is the fundamental mechanism behind weight loss — and GLP-1 medications like Mounjaro help by naturally reducing your appetite.
This calculator helps you understand what your deficit means in practical terms: how much weight you might lose per week and over a chosen timeframe.
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What this calculator does
Enter your maintenance calories and either a daily calorie target or a desired weekly weight loss. The calculator shows your daily deficit, weekly deficit, estimated weekly loss, and projected total loss over your chosen timeframe.
Who it is for
Adults on Mounjaro or other weight-loss medication who want to understand their calorie deficit and what it means for projected weight change. Also useful for anyone on a calorie-controlled diet.
How to use it
Enter your estimated maintenance calories (use our Mounjaro Calorie Calculator to find this). Then enter either a daily calorie target OR a desired weekly loss. Add a timeframe and your current weight for projected results. Click 'See My Result'.
How the calculation works
Daily deficit = maintenance calories − target calories. Weekly deficit = daily deficit × 7. Estimated weekly loss = weekly deficit ÷ 7,700 kcal/kg. Projected total loss = weekly loss × timeframe weeks. We flag deficits above 30% as aggressive and below minimum safe thresholds.
Worked example
Maintenance = 2,000 kcal, target = 1,600 kcal: Daily deficit = 400 kcal. Weekly deficit = 2,800 kcal. Estimated weekly loss = 0.36 kg. Over 12 weeks = projected loss of 4.4 kg. Starting at 90 kg, projected final weight ≈ 85.6 kg.
Assumptions and limitations
- Uses the simplified 7,700 kcal per kg of body weight model
- Does not account for metabolic adaptation (your body may burn fewer calories as you lose weight)
- Aggressive deficits (>30%) can cause muscle loss, fatigue, and nutritional deficiency
- Minimum safe calorie intake: 1,200 kcal/day for women, 1,500 kcal/day for men (general guideline)
- This is an estimate — actual results depend on many individual factors
Frequently asked questions
What calorie deficit is safe?
Most guidelines recommend a deficit of 15–25% below maintenance. Deficits above 30% are considered aggressive and may not be sustainable. Always discuss significant calorie restriction with a healthcare provider.
How much weight do you lose per 500 calorie deficit?
A 500 kcal/day deficit theoretically equates to about 0.45 kg (1 lb) per week. In practice, results vary due to metabolic adaptation and individual factors.
Can the deficit be too large?
Yes. Very large deficits can lead to muscle loss, fatigue, hair loss, and nutritional deficiency. Sustainable, moderate deficits combined with adequate protein intake are generally recommended.
Related calculators
- BMI Calculator for Mounjaro — Find your BMI, see which category it falls into, and understand how it relates to eligibility criteria for treatments like Mounjaro.
- Mounjaro Calorie Calculator — Calculate your maintenance calories and a safe deficit range to support steady weight loss alongside Mounjaro treatment.
- Mounjaro Protein Calculator — Find out how much protein you should aim for each day and per meal to support muscle preservation during weight loss on GLP-1 medication.
- Mounjaro vs Wegovy Calculator — Enter your weight and the monthly costs of each medication to compare projected weight loss, total spend, and cost per kilogram lost over yo
- Mounjaro Weight Loss Calculator — This planning tool projects how much weight you could lose over a chosen number of weeks, using conservative, moderate, or ambitious assumpt
Related guides
- Mounjaro vs Wegovy for Weight Loss — A balanced comparison of Mounjaro (tirzepatide) and Wegovy (semaglutide) — mechanism, effectiveness, cost, and side effects.
- How Much Weight Can You Lose on Mounjaro? — A realistic look at expected weight loss on Mounjaro (tirzepatide), based on clinical trial data and practical planning advice.
- How Much Protein Should You Eat on Mounjaro? — Why protein matters during GLP-1 weight loss and how to hit your daily target with practical meal guidance.
- How Many Calories Should You Eat on Mounjaro? — Understanding your calorie needs during Mounjaro treatment — maintenance, deficit, and safe intake ranges explained.
- What BMI Means for Weight-Loss Injections — How BMI is used to assess eligibility for weight-loss medications like Mounjaro and Wegovy, and its limitations.
Sources and references
NHS weight loss guidelines, NICE obesity guidance, Hall et al. body weight dynamics model
Last updated
Last reviewed: 2025-04-12.