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Weight Change Calculator

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Calculate the weight change and percentage change between a starting weight and a current weight. Add an optional selected weight to see the difference and the progress made towards it.

Your weights

kg
Used only to show the arithmetic difference and progress from the starting weight. It does not provide a recommended weight or timeframe. Enter it in the same unit as your current weight.

Result

Weight change from starting weight
6.7% decrease
Amount changed
6.0 kg decrease
Current weight as a share of starting weight
93.3% of starting weight

Selected-weight comparison

4.0 kg above selected weight

60% of the distance from starting to selected weight

Reference milestone

5%–9.9% decrease from starting weight

These are numerical reference milestones only. They do not assess whether a weight change is intentional, appropriate, healthy or safe for you.

Calculation only. This tool shows the numerical change between the weights entered. It does not assess whether weight change is intentional, appropriate, healthy or safe for you, and it does not diagnose a health condition.

Weight changes can have many causes. If weight loss is unintentional, rapid, ongoing or concerning—or if you are pregnant, under 18, have a history of an eating disorder, or have a medical condition or take medicines that affect weight—seek advice from a qualified healthcare professional.

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How to use this calculator

  1. Enter your starting weight, and pick its unit — kilograms, pounds, or stones and pounds.
  2. Enter your current weight, in the same range of units.
  3. Optionally enter a selected weight in the same unit as your current weight. It is used only for the arithmetic comparison below.
  4. Read the weight change from your starting weight, the amount changed, your current weight as a share of the starting weight, and the neutral reference milestone.
  5. Read the "Calculation only" limitation below the results before drawing any conclusion.

Nothing is submitted anywhere. The calculation runs in the page as you type.

What do I need to enter?

  • Starting weight — from 30 kg to 300 kg, or the same range in pounds or stones and pounds. The change is measured from it.
  • Current weight — the same range and units as the starting weight. It is compared with the starting weight.
  • Selected weight (optional) — a weight to compare against, in the same unit as your current weight. Leave it blank to skip the comparison.

What do the results show?

  • Weight change from starting weight — the percentage increase or decrease.
  • Amount changed — the difference in weight, in your current unit.
  • Current weight as a share of starting weight — current divided by starting, as a percentage.
  • Selected-weight comparison — how far above or below the selected weight you are, and how much of the distance from the starting weight you have covered.
  • Reference milestone — shown for a decrease only: less than 5%, 5%–9.9% or 10% or more. These are numerical bands, not clinical thresholds.

How weight change is calculated

The calculator converts all weights to a common unit before comparing them. It then calculates the numerical difference and percentage change from the starting weight.

Weight change = Current weight − Starting weight
Percentage change = (Current weight − Starting weight) ÷ Starting weight × 100

A negative result represents a decrease from the starting weight; a positive result represents an increase. Direction, the reference milestone, and every selected-weight comparison are decided from the raw converted values before any display rounding. The selected-weight comparison is optional and is arithmetic only — it is not a recommendation or a timeframe.

Worked example. Starting at 90 kg and now at 84 kg, the weight change is 84 − 90 = −6 kg, which is −6 ÷ 90 × 100 = 6.7% decrease — in the 5%–9.9% reference milestone. Your current weight is 84 ÷ 90 × 100 = 93.3% of the starting weight. With a selected weight of 80 kg, your current weight is 4.0 kg above it, and you have moved 60% of the distance from the starting weight to the selected weight.

Related tools

For a daily calorie estimate, see the weight loss calorie calculator or the weight gain calorie calculator.

Frequently asked questions

What does weight change percentage mean?

It is the difference between your current weight and your starting weight, expressed as a share of the starting weight: (current weight − starting weight) ÷ starting weight × 100. A negative result is a decrease from the starting weight; a positive result is an increase. Percentage puts a change on the same scale regardless of how much someone weighed to begin with.

How does the calculator handle an increase rather than a decrease?

The direction is decided from the raw converted weights before any rounding. If the current weight is above the starting weight, the result reads as an increase, the amount changed is shown as an increase, and the reference milestone reads "Weight increased from starting weight". The arithmetic is identical in both directions.

What do the 5% and 10% reference milestones mean?

They are numerical bands on the percentage decrease from the starting weight only: less than 5%, 5% to 9.9%, and 10% or more. They describe the size of the arithmetic change and nothing else. They are not clinical thresholds and not a personal health assessment — they do not tell you whether a change is intentional, appropriate, healthy or safe for you.

What does the selected weight comparison show, and is it a recommendation?

No. The selected weight is a number you choose as a mathematical reference point. When entered, the calculator shows the arithmetic difference between your current weight and the selected weight, and how far your current weight has moved from the starting weight towards it. It is not advice about what to weigh, and it does not predict when any weight would be reached.

Does this replace the weight loss percentage and weight gain percentage calculators?

Yes. Both were merged into this one calculator, which reports the difference and percentage change in either direction — a decrease or an increase — from the same starting weight and current weight. The old addresses now redirect here.

Why might an unintentional or concerning weight change need professional advice?

This tool only reports the numbers you enter. Weight changes can have many causes. If weight loss is unintentional, rapid, ongoing or concerning — or if you are pregnant, under 18, have a history of an eating disorder, or have a medical condition or take medicines that affect weight — a qualified healthcare professional can assess what is behind the change.

Last updated 25 October 2026.