How to Calculate Percentage of Weight Loss: The Formula, Worked Examples, and What the Numbers Mean Clinically

Key Takeaways

• The formula is: percentage weight loss = (starting weight minus current weight) divided by starting weight, then multiplied by 100.
• Example: starting weight 220 lbs, current weight 198 lbs. (220 minus 198) divided by 220 = 0.10. Multiply by 100 = 10 percent weight loss.
• The formula works the same in pounds, kilograms, or any other unit, as long as both weights use the same unit.
• 5 percent weight loss is the minimum threshold most clinical guidelines use for "clinically meaningful" weight loss.
• 10 to 15 percent loss substantially improves type 2 diabetes, sleep apnea, and cardiovascular markers; 20 percent or higher is the GLP-1 medication target.

Direct answer (40-60 words)

Percentage weight loss equals (starting weight minus current weight) divided by starting weight, multiplied by 100. Example: a 220-lb person who now weighs 198 lbs has lost (220 minus 198) divided by 220, equals 0.10, equals 10 percent. The formula works in any unit as long as both weights use the same unit.

Table of contents

1. The 30-second answer
2. The percentage weight loss formula explained
3. Worked examples in pounds and kilograms
4. Quick reference table for common starting weights
5. Why percentage matters more than total pounds lost
6. Clinical thresholds: 5 percent, 10 percent, 15 percent, 20 percent
7. How GLP-1 medications compare on percentage weight loss
8. Common mistakes when calculating percentage weight loss
9. Calculating percentage of body weight lost during a specific period
10. FAQ
11. Footer disclaimers

The percentage weight loss formula explained

The formula is straightforward:

Percentage weight loss = ((Starting weight - Current weight) / Starting weight) × 100

Percentage weight loss this period = ((Period start weight - Current weight) / Period start weight) × 100