Progress calculator
Weight Loss Percentage Calculator
See the change that matters across different starting weights, plus how far you have moved toward your own goal.
Enter the three useful numbers
10%
Percentage change makes progress comparable across different starting weights. Day-to-day scale noise matters less than the multi-week trend.
10% sits between Threshold usually called clinically meaningful (5%, a common care benchmark, not a trial result) and Semaglutide 2.4 mg (14.9%, STEP 1 mean at week 68).
These are averages across whole trial groups at 68 to 72 weeks. They are not a schedule, a target, or a prediction for one person, and landing somewhere else is not a failure.
The formula
Weight loss percentage equals starting weight minus current weight, divided by starting weight, multiplied by 100. The unit cancels, so the percentage is identical whether you use pounds or kilograms.
Measure the trend, not the morning
Hydration, sodium, carbohydrate intake, exercise, and digestion can move scale weight without changing body fat. Use consistent conditions and look across several weeks. Our smart-scale guide explains which measurements are useful and which deserve skepticism.
What the percentage means next to published trials
Percent of starting body weight is the unit obesity trials report in, which is why it is worth more than a subtraction. In STEP 1, mean weight change at week 68 was −14.9% with semaglutide 2.4 mg and −2.4% with placebo plus lifestyle support. In SURMOUNT-1 at week 72 it was −15.0%, −19.5% and −20.9% for tirzepatide 5 mg, 10 mg and 15 mg, against −3.1% for placebo. A reduction of about 5% is the threshold usually described as clinically meaningful.
The calculator places your figure among those means. Read them as what they are: averages over whole randomized groups across 68 to 72 weeks, in people meeting each trial's entry criteria. An average is not a schedule, not a target, and not a forecast for one person, and finishing above or below one says nothing about whether your own care is working.
Keep the quality of loss visible
A smaller number is not the only outcome. Strength, protein intake, movement, symptoms, sleep, and waist measurements add important context. Unexpected or excessive loss deserves clinical review, especially when accompanied by weakness or poor intake.
Straight answers
Frequently asked questions
How do you calculate weight loss percentage?
Subtract current weight from starting weight, divide by starting weight, then multiply by 100. For example, losing 20 pounds from 200 pounds is a 10% reduction in starting body weight.
Why use percentage instead of pounds?
A percentage puts the change in the context of your starting size. It is useful for comparing milestones over time, while pounds or kilograms are still helpful for day-to-day tracking.
How does my percentage compare with clinical-trial results?
Mean weight change was −14.9% at week 68 with semaglutide 2.4 mg in STEP 1 and −20.9% at week 72 with tirzepatide 15 mg in SURMOUNT-1, against −2.4% and −3.1% for the respective placebo groups. Those are averages for entire randomized groups over more than a year, not a rate anyone should expect week to week, and individual results within each trial varied widely.
How often should I weigh myself?
Choose a cadence you can use without distress and keep the conditions similar. Weekly averages or consistent weekly measurements can reduce the distraction of normal fluid shifts. Your clinician may recommend a different cadence.
Does the calculator measure fat loss?
No. Scale weight includes fat, lean tissue, water, glycogen, and digestive contents. A smart scale may help show a direction over time, but consumer body-composition estimates also have meaningful error.
Sources and method
Formula choices and health context were checked against the sources below in July 2026. Estimates are rounded so they stay practical.