See your monthly payment, what paying a little extra saves you, and where every dollar goes over the life of the loan.
Principal & interest is only part of it. These start as typical estimates: swap in your real tax rate, premium, and dues if you know them.
Add to your monthly payment and see how much sooner you're done, and how much interest you skip.
Your annual payment is the same every year. What changes is how much of it builds equity vs. covers interest.
Principal and interest are what the loan itself costs. Most lenders also collect property tax and homeowners insurance each month through an escrow account, and add private mortgage insurance when you put less than 20% down, plus any HOA dues you pay separately. The calculator shows the principal-and-interest figure and the full monthly cost side by side, because the second is the one your budget has to cover.
Every extra dollar goes straight to principal, so interest never accrues on it again. That is why a modest extra payment early in a 30-year loan can take years off the end and save a large share of the total interest. The extra-payments section shows the new payoff date and the interest saved for any amount you choose.
On a conventional loan you can ask the lender to cancel private mortgage insurance once the balance reaches 80% of the home's original value, and federal law ends it automatically at 78%, as long as your payments are current. FHA loans follow different rules.
A 15-year loan has a higher payment but usually a lower rate, and because the balance falls twice as fast it costs far less interest in total. A 30-year loan keeps the required payment lower, which leaves room in a tight budget, and you can still pay it down faster if you choose. How mortgages work walks through the tradeoff.