What actually makes up a mortgage payment

The principal-and-interest portion is fixed for the life of a fixed-rate loan, computed once from the loan amount, the rate per month and the number of months. Nothing about it changes when your home's value moves.

Property tax and insurance are separate escrow items that do change, which is why a payment can rise on a fixed-rate mortgage. When comparing lenders, compare principal and interest first and treat escrow as a local constant.

Interest each month is the outstanding balance times the monthly rate. At the start, the balance is at its largest, so interest swallows most of the payment and very little principal comes off. On a 30-year loan at 6%, roughly the first 18 years are interest-heavy before the split tips.

An amortisation schedule makes this concrete: read the interest column for month 1 against month 240 on the same loan and the crossover is obvious.

Extra money applied to principal removes all the future interest that balance would have generated. One additional monthly payment a year typically cuts four to six years off a 30-year term, because every early principal reduction compounds across the remaining schedule.

The saving is largest in the first decade and shrinks steadily afterwards, so timing matters more than size.

Run the payment at a rate one to two percentage points above the current quote. If that figure would break your budget, the offer relies on refinancing later - which may not be available.

Add tax and insurance in, then compare against take-home pay rather than gross. Lenders qualify on gross income, but you pay from net.