CFLib.org – Common Function Library Project

Description:
Calculate the number of payments for a loan when given the payment, interest rate, and value of the loan.

Return Values:
Returns a numeric value.

Example:

Number of Periods = <cfoutput>#Periods(0.08,20000,0,904.55)#</cfoutput>

Parameters:

Full UDF Source:

/**
 * Calculate the number of payments for a loan.
 * 
 * @param IR      Interest rate per year (8% = 0.08) 
 * @param PV      Present Value 
 * @param FV      Future Value 
 * @param PMT      Payment Amount 
 * @return Returns a numeric value. 
 * @author Raymond Thompson (rayt@qsystems.net) 
 * @version 1, August 2, 2001 
 */
function Periods(IR,PV,FV,PMT) {
  var tir = ir / 12;
  var scale = 0;
  var np=0;
  var tpv = -abs(pv);
  var tfv = -abs(fv);
  var tpmt = abs(pmt);

  if(ArrayLen(Arguments) gt 4) {
    scale = 10^abs(Arguments[5]);
  }
  np = log((-tfv * tir + tpmt) / (tpmt + tir * tpv)) / log(1 + tir);
  if (scale NEQ 0)
    np = int(np * scale + 0.5) / scale;
  return(np);
}