CFLib.org – Common Function Library Project

Description:
Calculate the payment on a loan given the interest rate, periods, and present value. The value returned is negative since the payment represents a reduction in the account. To get the simple value, call Abs on the result.

Return Values:
Returns a numeric value.

Example:

Payment = <cfoutput>#Payment(0.08,20000,0,24)#</cfoutput>

Parameters:

Full UDF Source:

/**
 * Calculate payment on loan.
 * 
 * @param IR      Interest rate per year (8.5% = 0.085) 
 * @param PV      Present Value 
 * @param FV      Future Value (Generally zero for calculating payments. Non zero for pay down to ammount.) 
 * @param NP      Number of periods. 
 * @return Returns a numeric value. 
 * @author Raymond Thompson (rayt@qsystems.net) 
 * @version 1, August 2, 2001 
 */
function Payment(IR,PV,FV,NP) {
  var tir = abs(ir) / 12;
  var tfv = abs(fv);
  var tpv = abs(pv);
  var scale = 0;
  var pmt=0;
  var q = (1 + tir)^ abs(np);

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