Method to calculate interpolation step value in Excel
Summary
The following Microsoft Excel formula performs linear interpolation by calculating the interpolation step value
=(end-start)/(ROW(end)-ROW(start))
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.
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.
More information
To create a sample linear interpolation formula, follow these steps:
1. Type the following values in a worksheet:
2. A1: 9 B1: =(A7-A1)/(ROW(A7)-ROW(A1))
3. A2: =A1+$B$1
4. A3:
5. A4:
6. A5:
7. A6:
8. A7: 11
9. Select cells A2:A6. On the Edit menu, point to Fill, and then click Down. The formula is filled down, and the following values are displayed in cells A2:A6:
10. A2: 9.33333
11. A3: 9.66667
12. A4: 10.
13. A5: 10.33333
14. A6: 10.66667
NOTE: You must type the reference to the step value in cell B1 as an absolute reference (with dollar signs).
