Every mortgage quote comes with two numbers that look similar but aren't: the interest rate and the APR. The interest rate is what your monthly principal-and-interest payment is actually calculated from. The APR folds in the lender's fees and points, spread out over the life of the loan, so it's usually a little higher — and it's the better number for comparing two loan offers apples-to-apples, since a lender advertising a lower rate can sometimes make it up in fees.
Why your early payments are mostly interest
A fixed-rate mortgage uses amortization: the total payment stays the same every month, but the mix between principal and interest shifts over time. Early on, you owe interest on nearly the full loan balance, so most of each payment goes toward interest and only a small sliver reduces what you owe. As the balance shrinks, more of each payment goes toward principal. On a 30-year loan, it's common for the crossover point — where you're finally paying more principal than interest — to land somewhere around year 15 to 20, depending on the rate. Our mortgage calculator shows this split for your specific numbers, and running the same loan amount at a 15-year term instead of 30 is a quick way to see how much interest a shorter term saves.
What actually moves your rate
- Credit score. This is usually the single biggest lever. The gap between a strong and a weak credit score can be a full percentage point or more on the same loan.
- Down payment size. A larger down payment lowers the lender's risk (and, below 20% down, usually triggers PMI — see below).
- Loan term. Shorter terms (15-year vs. 30-year) typically carry a lower rate, since the lender's money is at risk for less time.
- Discount points. You can pay an upfront fee ("buying points") to lower your rate for the life of the loan — worth it only if you'll hold the loan long enough for the monthly savings to outweigh the upfront cost.
- Broader market rates. Mortgage rates track the bond market, not the Fed's headline rate directly, so they can move for reasons that have nothing to do with your personal finances.
PMI: why it shows up, and how to lose it
Private Mortgage Insurance protects the lender, not you, when your down payment is under 20% of the home's value. It's typically rolled into your monthly payment as a percentage of the loan amount per year. The good news: PMI isn't permanent. Once your loan balance drops to 78% of the home's original value (through payments, or sooner if the home has appreciated and you request a new appraisal), lenders are generally required to drop it automatically, or you can ask them to reassess earlier.
Escrow: why taxes and insurance ride along with your payment
Most lenders roll your property tax and homeowners insurance into your monthly mortgage payment and hold the money in an escrow account, paying the actual bills on your behalf when they come due. It doesn't change how much tax or insurance you owe overall — it just smooths a once- or twice-a-year bill into twelve smaller pieces, which is why two homes at the identical loan amount and rate can still have noticeably different monthly payments once escrow is added in.
Fixed-rate vs. adjustable-rate mortgages
A fixed-rate mortgage locks your interest rate for the entire loan term — the payment you start with is the payment you keep (property tax and insurance can still shift the total, but the principal-and-interest portion never changes). An adjustable-rate mortgage (ARM) starts with a lower introductory rate for a set period — five or seven years is common — and then resets periodically based on a market index, which means the payment can go up or down after that initial period ends. ARMs can make sense if you're confident you'll sell or refinance before the adjustment period hits, but they carry real uncertainty if your plans change and you end up holding the loan into the adjustable phase during a period of rising rates.
How lenders decide how much you can borrow
Beyond your credit score, lenders lean heavily on your debt-to-income ratio (DTI) — your total monthly debt payments (including the new mortgage) divided by your gross monthly income. Most lenders want to see this land under roughly 43%, though the exact ceiling varies by loan type and lender. This is a big part of why two buyers with identical income can qualify for very different loan amounts: an existing car payment, student loans, or credit card minimums all count against you in this calculation, even though they have nothing to do with the home itself.