MORE: See our top picks for mortgage lenders right nowYahoo Finance mortgage calculatorA mortgage calculator can help you see how various mortgage term lengths and interest rates will affect your monthly payments. 30-year vs. 15-year fixed mortgage ratesGenerally, 15-year mortgage rates are lower than those for 30-year mortgages. When comparing 15- versus 30-year mortgage rates, know that the shorter term will save you money on interest in the long run. Adjustable rates sometimes start lower than fixed rates, but once the initial rate-lock period ends, you risk your interest rate going up. According to the latest forecasts, the MBA expects the 30-year mortgage rate to be near 6.50% through 2026.