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Weight Loss Percentage Calculator
Use this free weight loss percentage calculator to see how much of your starting weight you have lost, how far you still have to go, and when you are likely to reach your goal. Enter your starting weight, your current weight, and your target weight, pick pounds or kilograms, and the calculator shows your percentage lost, your remaining weight, and a goal-date projection at the weekly loss rate you choose.
Height is optional — leave it as is if you only want the percentage. It is used only to show how your BMI changes as you lose weight.
How the weight loss percentage works
The weight loss percentage answers a better question than "how many pounds have I lost?" — it asks how much of your starting weight that loss represents. Losing 20 lb means something different at 150 lb than at 250 lb, and the percentage captures that. Doctors use the same idea: a 5% to 10% loss from your starting weight is a common first target, because even that much can improve blood pressure, blood sugar, and how much load your knees carry.
Remaining to goal = current weight − target weight
Weeks to goal = remaining weight ÷ weekly loss rate
Those three lines are the whole calculator. Take your starting weight, subtract your current weight, divide by the starting weight, and multiply by 100. If you started at 200 lb and now weigh 180 lb, you have lost 20 lb, and 20 ÷ 200 × 100 = 10.0%. The remaining weight is just your current weight minus your target — 180 − 160 = 20 lb still to go — and dividing that by your weekly rate gives the time: 20 ÷ 1.5 = 13.3 weeks, or about 13 weeks, at 1.5 lb a week.
The weekly rate is where the plan meets reality. A loss of 0.5 to 2 lb (about 0.25 to 1 kg) per week is the range most health organizations call healthy and sustainable for most adults. The calculator defaults to 1.5 lb a week, which is brisk but inside that range. Picking 2 lb a week gives the earliest goal date, but it also asks the most of your eating and exercise habits every single week, and real progress is rarely a straight line — plateaus of two or three weeks are normal. If your projected date slips, it does not mean the plan failed; it usually means the rate was optimistic, and dropping the rate to 1 lb a week gives a more honest date.
The BMI change is a bonus view, not the main result. BMI is your weight in kilograms divided by your height in meters squared. At 68 inches tall (1.73 m), 200 lb (90.7 kg) gives a BMI of about 30.4, and 180 lb (81.6 kg) gives about 27.4 — a drop of 3.0 BMI points for the same 10% loss. The usual bands are under 18.5 underweight, 18.5 to 24.9 healthy, 25 to 29.9 overweight, and 30 or above obese. BMI is a rough screen, though: it cannot tell muscle from fat, so a very muscular person can have a high BMI while being lean. Use it as a trend line, and judge the plan mainly by the percentage lost and how you feel.
One more thing the percentage hides: daily weight bounces. Most people swing 1 to 4 lb day to day from water, salt, food still digesting, and hormones, which can easily mask a week's real fat loss. Enter a weekly average as your current weight, and judge the plan by the percentage over weeks, not by a single morning reading.
Worked example
Alex started at 200 lb, now weighs 180 lb, and wants to reach 160 lb, losing 1.5 lb a week. Alex is 68 inches tall. What has Alex achieved, and when will the goal arrive?
Step 1: Weight lost so far is 200 − 180 = 20 lb.
Step 2: The percentage lost is 20 ÷ 200 × 100 = 10.0%.
Step 3: Remaining to goal is 180 − 160 = 20 lb, which is 20 ÷ (200 − 160) = 50.0% of the way there.
Step 4: At 1.5 lb a week, the remaining 20 lb takes 20 ÷ 1.5 = 13.3 weeks — about 13 weeks from today.
Step 5: BMI at the start was 90.7 kg ÷ (1.727 m)² = 30.4; now it is 81.6 kg ÷ (1.727 m)² = 27.4, a drop of 3.0 points.
So Alex has lost 10.0% of the starting weight, is halfway to the goal, and should reach 160 lb in about 13 weeks at the chosen rate. Enter your own numbers above to see your percentage and your projected goal date.
FAQ
What is a healthy rate of weight loss per week?
Most health organizations consider 0.5 to 2 lb (about 0.25 to 1 kg) per week a healthy, sustainable rate for most adults. Faster loss is often mostly water in the first week or two, and very fast loss can cost muscle as well as fat. Slow, steady loss is easier to keep off, which is why this calculator defaults to 1.5 lb per week.
Why track weight loss as a percentage instead of pounds?
Because a percentage puts the loss in proportion to your starting size. Losing 20 lb is a 10% loss for someone who started at 200 lb, but a 13.3% loss for someone who started at 150 lb. Doctors often use a 5% to 10% loss as a meaningful target, because even that much can improve blood pressure, blood sugar, and joint load.
Why does my weight go up and down day to day?
Daily weight moves by 1 to 4 lb for most people because of water, food still digesting, salt, glycogen, and hormones. That is normal and it hides the slower fat-loss trend. Weigh yourself at the same time of day, in the same clothes, a few times a week, and compare weekly averages rather than single days.
What does the BMI change on this calculator mean?
BMI is your weight in kilograms divided by your height in meters squared. It is a rough screening number: under 18.5 is underweight, 18.5 to 24.9 is the healthy range, 25 to 29.9 is overweight, and 30 or above is in the obese range. BMI does not measure body fat directly and can misread very muscular people, so use it as a trend alongside the percentage lost, not as a verdict on its own.
When should I talk to a doctor about weight loss?
Talk to a doctor before starting a weight-loss plan if you have diabetes, heart disease, high blood pressure, an eating disorder, or take medication that affects weight, or if you are pregnant or breastfeeding. Also seek advice if you lose weight quickly without trying, or if you feel dizzy, very tired, or unwell while losing weight.