About the Weight Loss Percentage Calculator
Pounds and kilograms tell you how much weight you have lost, but not how much it means for your body. Losing 10 lb is a big change for someone who started at 130 lb and a smaller one for someone who started at 260 lb. That is why doctors, dietitians, clinical trials and weight loss challenges measure progress as a percentage of starting body weight.
This weight loss percentage calculator works out the percentage of your body weight you have lost, the amount in pounds or kilograms, how far you are toward a goal weight, and, if you enter the number of weeks, your weekly rate of loss as both an amount and a percentage. It also shows a gain clearly if your weight has gone up.
How to Use the Weight Loss Percentage Calculator
Choose lb or kg.
Enter your starting weight, the weight when you began, and your current weight.
Optionally enter a goal weight to see your progress toward it, and the weeks since you started to see your weekly rate.
The Formulas
weight lost = starting weight − current weight
% of body weight = weight lost ÷ starting weight × 100
goal progress = weight lost ÷ (starting weight − goal weight) × 100
weekly rate = weight lost ÷ weeksStep-by-Step Example
A starting weight of 200 lb, a current weight of 180 lb and a goal of 170 lb, after 10 weeks.
weight lost = 200 − 180 = 20 lb
percentage = 20 ÷ 200 × 100 = 10% of body weight
goal progress = 20 ÷ (200 − 170) = 20 ÷ 30 = 66.7%, with 10 lb to go
weekly rate = 20 ÷ 10 = 2 lb a week, 1% of starting weight per weekIn kilograms: from 90 kg to 85.5 kg is a 4.5 kg loss, and 4.5 ÷ 90 × 100 = 5% of body weight.
How to Calculate Weight Loss Percentage by Hand
You only need two numbers and a calculator. Subtract today's weight from your starting weight to get the amount lost, divide that by the starting weight, then multiply by 100. Always divide by the starting weight, not the current one; dividing by the current weight makes the percentage look larger than it is. For 200 lb to 180 lb, dividing by 180 would give 11.1% instead of the correct 10%.
Why Percentage Matters for Health
Research on weight and health often uses percentage targets. Losing 5% of body weight is associated with measurable improvements for many people who are overweight, such as lower blood pressure, better blood sugar control and lower triglycerides. Losing 10% tends to bring larger benefits, including for joint pain and sleep apnoea. These targets are much more achievable than a final goal weight, so they are useful milestones on the way.
Percentages for Weight Loss Challenges
Workplace and gym weight loss challenges usually rank people by percentage lost rather than pounds, so that a smaller person is not at a disadvantage against a larger one. Use the same starting weigh-in for everyone, weigh at the same time of day in similar clothing, and compare the percentages at the end.
A Healthy Rate of Loss
A common recommendation is to lose about 0.5 to 1% of body weight per week, roughly 1 to 2 lb a week for a 200 lb person or 0.5 to 0.9 kg a week for a 90 kg person. Losses are often faster in the first couple of weeks, when water and stored carbohydrate are lost, and slower later as the body adapts and energy needs fall. Losing much faster than 1% a week is harder to sustain and tends to remove more muscle along with fat.
Daily Ups and Downs
Body weight can change by 1 to 2 kg from one day to the next because of water, salt, the food in your digestive system, exercise and hormones. A single high reading does not mean you have gained fat. For a fair percentage, weigh yourself at the same time each day, ideally in the morning after using the bathroom, and use the average of several days or a weekly weigh-in.
Beyond the Scale
Weight is only one measure. If you are strength training, you may lose fat while gaining some muscle, so your weight changes slowly even as your body changes a lot. Waist measurements, how clothes fit, fitness and blood test results all give useful extra information alongside the percentage.
Weight Loss Percentage Chart
How many pounds equal common percentage milestones at different starting weights.
| Starting weight | 5% | 10% | 15% | 20% |
|---|---|---|---|---|
| 150 lb | 7.5 lb | 15 lb | 22.5 lb | 30 lb |
| 180 lb | 9 lb | 18 lb | 27 lb | 36 lb |
| 200 lb | 10 lb | 20 lb | 30 lb | 40 lb |
| 250 lb | 12.5 lb | 25 lb | 37.5 lb | 50 lb |
| 300 lb | 15 lb | 30 lb | 45 lb | 60 lb |
In kilograms, 5% of 80 kg is 4 kg and 10% is 8 kg; 5% of 100 kg is 5 kg and 10% is 10 kg.
Understanding Your Result
The headline gives the percentage of your starting weight you have lost, or gained.
The amount line gives the change in pounds or kilograms.
The goal progress line shows how far you are toward your goal weight and how much is left.
The weekly rate line gives your average loss per week, as an amount and as a percentage.
When Should You Use This Calculator?
Use it to track progress in pounds or kilograms as a percentage.
Use it to check whether you have reached a 5% or 10% milestone.
Use it to compare results fairly in a weight loss challenge.
Common Mistakes
Dividing by the current weight. Always divide by the starting weight.
Comparing single weigh-ins. Use weekly averages to smooth out water changes.
Mixing units. Use kilograms or pounds for every weight, not both.
Judging only by the scale. Measurements and fitness matter too.