Brian Dunning's FileMaker Custom Functions

IRR ( IRR1 ; IRR2 ; NPV1 ; NPV2 )

IRR - Calculate the IRR through 'Interpolation'

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Barry Maskell   Barry Maskell
CB Richard Ellis

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  Sample input:
IRR ( 11 ; 12 ; 35167 ; 54790 )
  Sample output:

  Function definition: (Copy & paste into FileMaker's Edit Custom Function window)

Where the IRR is required without the use of a spreadsheet or as a check method, the IRR for a project can be calculated through INTERPOLATION, through simple linear interpolation. This involves finding the IRR of two trials where the NPV is either side of zero. Then by using the interpolation formula, the IRR can be found.

Eg: IRR1 = 11%
IRR2 = 12%
NPV1 = $35,167
NPV2 = $54,790
RESULT IRR : 11.36%



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