Bariatric Weight Loss Calculator

A bariatric weight loss calculator is a medically designed tool that estimates how much weight a patient may lose after bariatric surgery, such as a gastric sleeve, bypass, or duodenal switch.

It uses your current weight, height, age, and procedure type to project your BMI, ideal weight, and expected monthly progress over 12–18 months.

If you’ve ever wondered, “How much weight will I lose with a gastric sleeve?”  this calculator gives you a science-based answer.

How It Works: The Formula Explained

Our bariatric surgery weight loss calculator combines real medical data and evidence-based formulas used by bariatric specialists.

1. BMI (Body Mass Index)

​BMI = Weight (kg) / [Height (m)]²​

This shows whether your body is underweight, healthy, overweight, or obese.

2. Ideal Weight – Divine Formula

Ideal Weight (kg) = 50+2.3×(Height (in) – 60)

This helps estimate how much weight you need to lose to reach a healthy BMI.

3. Excess Weight

Excess Weight = Current Weight–Ideal Weight

4. Expected % Excess Weight Loss (EWL%)

Based on clinical data (MBSAQIP, ASMBS):

5. Projected Weight Loss Over Time

The calculator spreads weight loss evenly across 1–18 months, showing how your bariatric weight loss by month may look on a progress chart.

Example:
If your excess weight = 80 lbs and your EWL = 70%, you could expect to lose about 56 lbs over 12–18 months — roughly 3–5 lbs per month in the early stages.

Example: Gastric Sleeve Weight Loss

Let’s say:

• Current weight: 250 lbs

• Height: 5’6″ (66 in)

• Surgery: Gastric Sleeve

BMI: 40.3
Ideal Weight: 142 lbs
Excess Weight: 108 lbs
Expected EWL (65%) → 70 lbs lost in 12–18 months

That’s exactly what our gastric sleeve weight loss calculator estimates.

Benefits of Using This Calculator

✅ Accurate medical data (Devine & MBSAQIP formulas)
✅ Personalized monthly progress graph
✅ Option to download results as PDF
✅ Works for bariatric sleeve, bypass, duodenal switch, and band
✅ Mobile-friendly, ADA-compliant, and privacy-safe

Bariatric Weight Loss by Month

You can use the bariatric weight loss calculator by month to visualize this journey and stay motivated.

Why Accuracy Matters

Other tools like the Mexico Bariatric Center Weight Loss Calculator offer general estimates, but our version provides a realistic and personalized timeline using evidence-based parameters and visual charts.
That’s why it’s often referred to as the bariatric surgery expected weight loss calculator — trusted by both patients and doctors.

Frequently Asked Questions

Q1: How much weight will I lose after bariatric surgery?
It depends on your procedure type and lifestyle. Most patients lose 60–80% of their excess weight within 12–18 months. Use the calculator for a custom estimate.

Q2: How does the bariatric calculator weight loss formula work?
It uses BMI and EWL% (Excess Weight Loss Percentage) based on surgical averages to project your timeline.

Q3: Can I use it for the gastric sleeve only?
Yes — it’s also a bariatric sleeve weight loss calculator specifically tuned for sleeve gastrectomy patients.

Q4: Does it work for revisional or mini bypass surgeries?
Yes, but results vary — always consult your bariatric surgeon for personalized guidance.

Medical Disclaimer

Important: The Bariatric Weight Loss Calculator provides estimates only. It is not a substitute for professional medical advice, diagnosis, or treatment.
Results are based on general averages from published bariatric outcomes and may vary depending on individual factors such as surgery technique, adherence to diet and exercise, and underlying health conditions.
Always consult your bariatric surgeon, physician, or a qualified healthcare provider before making any medical or dietary decisions.

Usage Warning

• Do not rely on this calculator for clinical or surgical decisions.

• Data entered here is not stored or transmitted.

• This tool is intended for educational purposes only.