You can save a significant amount of mortgage interest paid if you make one additional principal and interest payment a year this will reduce a $30$ year mortgage by around six years it also increases your equity in the home faster if you choose to pay one additional mortgage payment a year by paying $1/12$ of it each month makes certain to know the extra money is to reduce principal how much will you pay each month for a Margaret mortgage of $$152,000$ at $3\mathrm{.}50\%$ for $16$ years