The calculator, which is available from today, will display the impact of any increase or decrease in the mortgage rate and calculate payments on a part and part method of repayment.
Brokers will also be able to save the results as a PDF file.
Santander has made several changes to its lending criteria and introduce a number of new initiatives in recent months.
Just this week, the lender removed its tiered approach to affordability for buy-to-let customers, introducing a single stress rate of 5.5% applied to all deals up to and including 75% loan-to-value. At the same time it increased its rental cover ratio from 125% to 145%.
In September, Santander also introduced a 30 minute online service for remortgage customers, which it plans to roll out to home movers and first-time buyers by year end.
