Weight change percentage calculator
Enter your starting weight and your weight now. You see the change as a percentage of where you started, in kilograms or pounds, and per week if you add how long it took.
Updated
Simple arithmetic on the numbers you enter. Day-to-day weight moves with water, food and time of day, so compare weigh-ins taken the same way.
The formula this calculator uses
Change
change = weight now − starting weight, in the unit you chose.
Percentage (large number)
change % = change ÷ starting weight × 100, shown to one decimal with a + or − sign.
Per week and share of start
per week = change ÷ weeks (two decimals) · now as % of start = weight now ÷ starting weight × 100.
Worked examples
Each row was entered into this calculator and the result copied as shown.
| Entry | Change, % of start | Change | Per week | Now as % of start |
|---|---|---|---|---|
| 100 kg → 92 kg · 10 weeks | −8 | −8 kg | −0.8 kg a week | 92% |
| 80 kg → 84 kg · 4 weeks | +5 | +4 kg | +1 kg a week | 105% |
| 220 lb → 209 lb · 12 weeks | −5 | −11 lb | −0.92 lb a week | 95% |
What this calculator does not do
- It does not say whether your change is healthy, expected or too fast.
- It does not compare you with trial results for any medication.
- It does not smooth out day-to-day ups and downs; it uses the two numbers you type.
- It does not store weigh-ins; PepLabo’s weight log does that.
About this estimate and your privacy
A percentage is useful because it scales with your starting point: the same 5 kg is a different share of 70 kg than of 140 kg. It says nothing about what the change means for your health; that is for your clinician.
Everything is worked out by a script inside this page. The script makes no network requests, the page’s security policy (Content-Security-Policy with default-src none and no connect-src) would block them anyway, and nothing you type is stored, not even in your browser’s storage. Reload the page and the fields are empty again.
Next to each source below is what it supports on this page.
Zepbound® is a trademark of Eli Lilly and Company. PepLabo is not affiliated with or endorsed by Eli Lilly and Company.
Questions
Why use a percentage instead of kilograms?
A percentage makes changes comparable between people of different sizes and over time. The Zepbound® label, for example, lists mean percent change in body weight as a primary efficacy measure [2].
Is a 5% change meaningful?
The CDC notes that even modest weight loss can help improve blood pressure, cholesterol and blood sugar, and uses 5% of 200 lb (10 lb) as an example [1]. What it means for you is a question for your clinician.
Why do medication trials report the share of people losing 5%?
In the Zepbound® trials, the primary efficacy measures were mean percent change in body weight and the percentage of patients reaching at least 5% weight reduction [2]. It is a way to describe a group, not a personal target.
What pace does the CDC call gradual?
About 1 to 2 pounds a week, and the CDC says people who lose weight at that pace are more likely to keep it off [1].
Which starting weight should I use?
Whatever point you want to measure from: the day you started a program, a clinic visit or the start of the year. PepLabo keeps every weigh-in, so you can pick any of them.
Does it work in pounds?
Yes. Choose lb; the percentage is the same either way because both weights use the same unit.
What if my weight went up?
The result is shown with a + sign and "gained". The arithmetic is the same.
Can I see this in PepLabo?
Yes. Log your weigh-ins in PepLabo and the trend line shows how your weight moves over the range you choose, with your goal weight as a dashed line.
Sources
Sources checked on
- CDC. Steps for losing weight Supports: 5% of 200 lb as an example; modest weight loss and blood pressure, cholesterol, blood sugar; 1 to 2 lb a week as gradual.
- Zepbound® (tirzepatide) injection: US prescribing information, Eli Lilly and Company (DailyMed) Supports: mean percent change and share reaching ≥5% weight reduction as primary efficacy measures.
Set up your lab tonight.
It takes a few minutes. Pep will be waiting.