# Microsoft Office Application Help - Excel Help forum > Excel Formulas & Functions >  >  How to use the Linear Interpolation Formula in Excel 2010

## emmanuelsekimpi

Given that (x) represents hours worked for and (y) represents salaries paid for the hours worked.

(x)          (y)
360 ->3,500,000
240 ->?
180 ->?
120 ->?
60 ->1,000,000
Using the Linear Interpolation function y2 = (x2-x1)(y3-y1)/(x3-x1) + yi, I want to arrive at a general Excel formula that I will always use in Excel 2010 to compute for salaries of employees depending on the number of hours worked.

Kind Regards,

Emma.

----------


## XOR LX

You can use the FORECAST function which uses the linear interpolation you require. You will only need to arrange your data slightly differently so that your known values appear in consecutive rows, i.e. 

360	→	3,500,000
060 	→	1,000,000
240	→	
180	→	
120	→	

Assuming the value 360 is in cell A1 and 3,500,00 is in cell B1, then to get the linear interpolation for 240, 180 and 120, type the following formula in cell B3 and copy down:

=FORECAST(A3,$B$1:$B$2,$A$1:$A$2)

If you insist on having your data in the below form (i.e. with your known values at the top and bottom of your dataset) and/or are interested in representing the linear interpolation formula in full in Excel, in cell B2 type the following formula and copy down as required:

=B$5+((B$1-B$5)*(A2-A$5)/(A$1-A$5))

360	→	3,500,000
240	→	
180	→	
120	→	
060	→	1,000,000

Regards

----------

