Weight Loss Percentage Calculator

percent lost = (starting weight − current weight) ÷ starting weight × 100 · percent of goal = (starting weight − current weight) ÷ (starting weight − target weight) × 100

starting weight

The weight you began this attempt at. It is the denominator, which is why it is asked for separately (kg)

current weight

The weight you are at now, in kilograms (kg)

target weight

The weight you are aiming for, in kilograms (kg)

Use it when you want to know how far you have come, or to compare a loss fairly between two people of different sizes, or to check a claim in the press — most published figures about weight loss are percentages of starting weight, and a kilogram count on its own will not tell you whether a study's result was large. It is also the right page when you have been losing for a while and the kilogram numbers have stopped feeling like progress; the percentage keeps the same meaning as the starting weight falls, which the raw number does not.

1. Started at 90 kg, now 82.5 kg, aiming for 80 kg

   1. Weight lost: 90 − 82.5 = 7.5 kg
   2. Percent of starting weight: 7.5 ÷ 90 × 100 = 8.3 per cent
   3. Total the goal asks for: 90 − 80 = 10 kg
   4. Percent of goal: 7.5 ÷ 10 × 100 = 75 per cent
   5. Still to lose: 82.5 − 80 = 2.5 kg

   Three quarters of the way there, and the two percentages are read off different denominators — 8.3 per cent of the body, 75 per cent of the plan. Watching only the first one understates how far through the job this is.

2. Started at 100 kg, now 90 kg, target reached

   1. Weight lost: 100 − 90 = 10 kg
   2. Percent of starting weight: 10 ÷ 100 × 100 = 10 per cent
   3. Total the goal asked for: 100 − 90 = 10 kg
   4. Percent of goal: 10 ÷ 10 × 100 = 100 per cent
   5. Still to lose: 0 kg

   Ten per cent of starting weight is the figure the diabetes prevention trials used as their target, which makes this the case where the percentage and the clinical literature line up exactly.

A percentage of starting weight flatters whoever started heavier, and that is not a flaw in the arithmetic — it is the property that makes it useful for comparison and useless as a score. It also says nothing about what was lost: early weight is largely water and glycogen, later weight is a mix of fat and lean tissue, and two people at the same percentage can be in very different places depending on how fast they got there. This page cannot tell you whether the rate is sensible; the weight loss calculator applies the published guidance on pace, and this one deliberately does not. Reaching the goal is not the same as keeping it — most of the weight that comes back does so within a year, and nothing in these four numbers predicts whether you will be the exception. If your target weight is itself below a healthy range for your height, a hundred per cent on this page is not a good outcome, and the healthy weight calculator is the page that says so.

How do you calculate weight loss percentage?

Divide the kilograms you have lost by the weight you started at, then multiply by a hundred. Someone who began at 90 kg and is now 82.5 kg has lost 7.5 kg, which is 7.5 ÷ 90 = 8.3 per cent. The denominator is always the starting weight and never the target or the current one: dividing by the target gives a bigger, better-looking number that no study or guideline would recognise, and dividing by the current weight gives a figure that changes every time you step on the scale.

What is a good percentage of weight loss?

Five per cent is the point at which the clinical literature starts reporting measurable improvements in blood pressure and blood sugar, and ten per cent is the target the large diabetes prevention trials used — both are worth aiming at and neither requires reaching a goal weight. Beyond that, the useful question stops being how much and becomes how fast, because rapid loss takes lean tissue with it. A percentage is a description of progress, not a grade.

Why is my percentage smaller than my friend's when we lost the same amount?

Because you started heavier. Ten kilograms off a starting weight of 60 kg is 16.7 per cent; the same ten kilograms off 120 kg is 8.3 per cent. The body that lost the larger share had less to spare, which is exactly why the percentage is the fairer comparison across people — and also why it is a poor way to compare your own progress at two different points in the same attempt.

What does the percentage of goal figure mean?

It is the share of the distance between your starting weight and your target that you have already covered, so it starts at zero and reaches a hundred when you arrive. It uses a different denominator from the percentage lost — the total the goal asks for rather than the whole body — and the two will not match. If you pass the target it keeps going above a hundred, and if you set the target to where you started it returns zero, because a journey with no distance has no completion to report.

Should I track this instead of kilograms?

Use both, for different jobs. The kilogram figure is what a scale shows and what a clinician will ask about; the percentage is what stays comparable as the starting weight falls and what lets you read a study's result or a guideline's target. What neither captures is body composition — a percentage of body weight lost can include a lot of muscle, and the tape measure and the body fat pages are the ones that would show it.

• Losing weight — healthy weight growth — US Centers for Disease Control and Prevention
• Clinical Guidelines on the Identification, Evaluation, and Treatment of Overweight and Obesity in Adults — National Heart, Lung, and Blood Institute (US), 1998