Free Excel & Sheets Interpolation Template

One workbook with a ready-made sheet for every common interpolation job.

  • Linear: two points in, y out, with a chart.
  • Table: up to 1,000 data rows and 500 lookups at once.
  • Double (2D): laid out like a steam table.
  • Inverse: find x for a given y.

Plain formulas, no macros. Works in Excel 2010+ and LibreOffice. For Google Sheets, use File → Import.

Download (.xlsx, free)

Just need the Excel formula?

Between two rows (x₁, y₁ in A2:B2, x₂, y₂ in A3:B3, x in D2):

=B2+(D2-A2)*(B3-B2)/(A3-A2)

In a sorted table A2:B100 (Excel 365):

=LET(x,D2, xs,A2:A100, ys,B2:B100, i,MATCH(x,xs,1),
  x1,INDEX(xs,i), x2,INDEX(xs,i+1), y1,INDEX(ys,i), y2,INDEX(ys,i+1),
  y1+(x-x1)*(y2-y1)/(x2-x1))