Weight loss percentage calculator
Enter your starting and current weight; the calculator returns the percentage of body weight you have lost and where that sits against the clinical benchmarks. 5% is the threshold used in FDA approvals and obesity guidelines; the big GLP-1 trials averaged roughly 15% (semaglutide, 68 weeks) and up to 21% (tirzepatide, 72 weeks) — over more than a year, not a month.
Calculator
The formula
Percentage lost = (starting weight − current weight) ÷ starting weight × 100. Units cancel out, so it works identically in pounds or kilograms.
What the percentages mean
| Milestone | What it corresponds to |
|---|---|
| 5% | The "clinically meaningful" benchmark used in FDA approvals and obesity guidelines — measurable improvements in blood pressure, glucose and lipids. |
| 10% | Associated with larger metabolic improvements; a common second treatment target. |
| ~15% | Average loss with semaglutide 2.4 mg at 68 weeks in STEP 1. |
| ~21% | Average loss with tirzepatide 15 mg at 72 weeks in SURMOUNT-1. |
Trial averages are just that — averages of thousands of people over more than a year, alongside diet and activity changes. Individual results spread widely around them in both directions.
Sources
- STEP 1: Once-weekly semaglutide in adults with overweight or obesity (NEJM, 2021)
- SURMOUNT-1: Tirzepatide once weekly for the treatment of obesity (NEJM, 2022)
- Wegovy FDA label
Track the trend, not one weigh-in
Bo logs your weight, syncs it two-way with Apple Health, and shows the trend line next to your doses — so you can see what is actually moving the number.
Educational information only. Bo is a tracking app, not a medical device, and nothing here is medical advice, a dosing recommendation, or a substitute for your prescriber. Half-lives are population averages from the sources cited on each row; individual clearance varies with body weight, kidney and liver function, and other medication.