Definition of 'Conversion Option'
A clause associated with some adjustable-rate mortgages that allows the borrower to convert the variable interest rate to a fixed rate within a certain time period, or at certain future dates. The conversion option is not free; an adjustable-rate mortgage with a conversion option will typically have a higher margin, and therefore higher fully indexed interest rate, or higher costs than an adjustable-rate mortgage without a conversion option.
Investopedia explains 'Conversion Option'
To analyze the economics of a conversion option, borrowers should total up the cost of the conversion option (an initial higher interest rate and/or higher loan costs) plus the cost of the actual conversion to a fixed rate, then compare this total to the costs of refinancing into a fixed interest rate at a future date.
Remember that a fee must often be paid to convert to the fixed rate, and the fixed rate that the ARM is converted to is typically based upon the market rate at the time of conversion plus a certain percentage. If the future refinancing costs are estimated to be less than the total costs of the conversion option, then the conversion option is not economical. The borrower would be better off with a traditional ARM with the intent to refinance into a fixed interest rate at a future date.