Weight loss percentage calculator

Express a weight change as a percentage of starting weight.

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Weight loss percentage calculator processes your input in this browser. Inputs and results are excluded from analytics. Recent tools save tool names, visit counts and last-visit times. Saved tools store only their names. Draft saving is optional and stays on this device; delete saved text with the draft controls. Loading text from a URL is optional and contacts that server; its URL and your IP address are visible to the server. An optional “Use in” action keeps a handoff in this tab. The next tool removes it on arrival and ignores it if more than a minute has passed.

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Starting weight

Current weight

Answer

…

Percentage of starting weight lost = (starting weight − current weight) ÷ starting weight × 100.

More results

Precision and calculation record

Decimal places in numeric results and text downloads

Rounding changes displayed numbers, not the calculation. Text, fractions, matrices and CSV schedules keep their own formatting. Automatic keeps up to 12 significant digits, with money shown to cents where applicable.

Step-by-step calculation

Inputs are substituted below. Each line evaluates the next operation; intermediate values are displayed to 12 significant digits while the calculation uses full precision.

Saved scenario

Save the current answer, then change an input to compare. This clears when you leave.

Formula and assumptions

Both weights must use the same unit. A negative result means a gain. This describes a change only; it does not set a goal or assess whether the change is healthy.

Automatic precision shows numbers to 12 significant digits. Thousands separators such as 1,000 are accepted; use a dot for decimals.

Scratch calculator

Check another calculation

Use +, −, ×, ÷, parentheses and %. A percentage is divided by 100. This does not change the main tool.

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Updated 2026-09-26

Using Weight loss percentage calculator

Percentage of starting weight lost = (starting weight − current weight) ÷ starting weight × 100.

Both weights must use the same unit. A negative result means a gain. This describes a change only; it does not set a goal or assess whether the change is healthy.

Next: Basic calculator

A worked example

With starting weight = 200, current weight = 190, the weight lost (%) is 5.

Before you use the result

Both weights must use the same unit. A negative result means a gain. This describes a change only; it does not set a goal or assess whether the change is healthy.

Example results for starting weight

These examples use Current weight: 190. They are reference calculations, not recommended settings.

Starting weight	Weight lost (%)
100	-90
200	5
400	52.5

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ToolOctopus. “Weight loss percentage calculator.” Updated 2026-09-26. https://tooloctopus.com/weight-loss-percentage-calculator.

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