About the Index Number Calculator
Rebase a series to an index (base period = 100) to compare growth of values on different scales.
Also known as: index calculator, base 100 index, rebasing index.
How to use this calculator
- Enter values, base period (position).
- The result updates instantly as you type — press Calculate (or Enter) at any time.
- Review the breakdown shown under the main result.
- Use Copy result or Share to save the answer or send a link with your inputs.
Formula
Index = value ÷ base value × 100
Worked example
Using the values pre-filled in the calculator above:
- Values: 250, 262, 270, 295, 310
- Base period (position) = 1
the calculator returns:
- Latest index: 124