The following Microsoft Excel formula performs linear interpolation bycalculating the interpolation step value
where end is the cell address of the larger number, and start is the cell address of the smaller number.
Interpolation is a method used to determine a present or future value factor when the exact factor does not appear in either a present or future value table. Interpolation assumes that the change between two values is linear and that the margin of error is insignificant.
To create a sample linear interpolation formula, follow these steps: