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Weight Loss Percentage Calculator

Calculate what percentage of your body weight you have lost, your weekly rate, progress towards a goal weight and a projected goal date.

What is the Weight Loss Percentage Calculator?

Weight loss percentage is (starting weight − current weight) ÷ starting weight × 100. Going from 90 kg to 81 kg is a 10% loss. Percentage is the fairer comparison between people because it scales with body size.

  • Percentage lost, absolute change and weekly average in one view
  • Progress bar towards a goal weight with a projected date
  • Rate banded against your current weight, not a fixed number
  • Kilogram, pound and stone units that convert as you toggle
  • Handles weight gain honestly instead of showing a negative loss
  • Fully offline — your weights and dates never leave your browser

How to use the Weight Loss Percentage Calculator

  1. 1

    Choose kilograms, pounds or stone.

  2. 2

    Enter your starting weight and your current weight.

  3. 3

    Add a goal weight, or set it to zero to skip the goal section.

  4. 4

    Pick whether the weekly rate comes from your weigh-in dates or a rate you type.

  5. 5

    Read your percentage lost, weekly rate and projected goal date.

About the Weight Loss Percentage Calculator

The ByteTools Weight Loss Percentage Calculator turns two weigh-ins into the number people actually want: the percentage of your starting weight you have lost. It also gives the absolute change in kilograms and pounds, your average rate per week, how far along you are towards a goal weight, and a projected date for reaching it.

The weekly rate can come from the dates of the two weigh-ins, or you can type in a rate you already know. It is banded against your current weight — roughly 0.5 to 1 percent of body weight per week is the range most guidelines describe as sustainable — so you can see at a glance whether the pace is fast, typical or slow. Kilograms, pounds and stone are all supported and convert as you switch.

Everything is computed in your browser and no weights or dates are uploaded or stored. These are estimates only and not medical or nutritional advice. Scale weight swings by a kilogram or two with hydration, salt and glycogen alone, and percentage loss says nothing about how much of the change was fat rather than muscle, so speak to a doctor or a registered dietitian before a substantial weight-loss plan.

Frequently asked questions

How do you calculate weight loss percentage?

Subtract your current weight from your starting weight, divide by the starting weight, and multiply by 100. Going from 90 kg to 81 kg gives 9 ÷ 90 × 100, which is a 10% loss. The units cancel, so it works identically in pounds or stone.

What is a healthy rate of weight loss?

Most guidelines describe roughly 0.5 to 1 percent of body weight per week as sustainable — around 0.5 to 1 kg per week for someone at 100 kg, and proportionally less for someone lighter. Faster loss tends to cost more muscle and is harder to maintain, though medically supervised programmes sometimes go faster on purpose.

How accurate is a projected goal date?

It is a straight-line extrapolation, which is the weakest assumption on the page. Real weight loss slows as you get lighter, because a smaller body needs fewer calories and adherence usually drifts, so treat the projected date as the earliest plausible one rather than a schedule. Recalculate every few weeks with fresh numbers.

Why use percentage instead of kilograms lost?

Because it scales with body size. Losing 5 kg from 120 kg and losing 5 kg from 60 kg are very different achievements physiologically, and percentage puts them on a common footing. It is also the metric clinical studies and weight-management programmes normally report.

What is 5% weight loss and why does it matter?

Five percent of your starting weight — 4.5 kg for someone starting at 90 kg. It is a commonly cited threshold because clinical trials find meaningful improvements in blood pressure, blood glucose and blood lipids at around that level, well before anyone reaches a cosmetic goal.

Why does my weight fluctuate day to day?

Hydration, sodium intake, stored glycogen, hormones and the contents of your gut can move the scale by one to two kilograms within a single day, which is easily 2% of body weight. Weigh yourself at the same time of day under the same conditions, and pay attention to the weekly average rather than any single reading.

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