When most people think about their mortgage payment, they picture the monthly amount they write a check for. What they often do not realize is that payment is made up of four separate components — and understanding each one is essential to knowing whether you have a good deal.
The Four Parts of PITI
- •Principal: The portion of your payment that reduces your actual loan balance. In early years of a 30-year mortgage, this is often less than 30% of your payment.
- •Interest: The cost of borrowing. In early years, over 70% of your payment goes here — which is why the first years of a mortgage build equity slowly.
- •Taxes: Property taxes are usually escrowed (held by your lender and paid on your behalf). They vary wildly — from under 0.5% of home value in some states to over 2% in others.
- •Insurance: Homeowner's insurance is almost always required. PMI (private mortgage insurance) is added if your down payment is under 20% and typically costs 0.5–1.5% of the loan annually.
How Amortization Works
Amortization is the process of spreading loan repayment over time in fixed installments. Your monthly payment stays the same — but the split between principal and interest shifts dramatically over time.
On a $400,000 mortgage at 7% for 30 years, your payment is approximately $2,661/month. In month 1: $2,333 goes to interest, $328 goes to principal. In year 15: roughly $1,900 to interest, $761 to principal. In year 29: mostly principal. This is why refinancing in year 25 often does not make financial sense — you have already paid most of the interest.
Calculate Your Mortgage
15-Year vs. 30-Year Mortgage
On the same $400,000 loan at similar rates, the 15-year mortgage typically offers a rate 0.5–0.75% lower than the 30-year. The payment is higher — but the total interest paid is dramatically less:
- •30-year at 7.00%: $2,661/month · Total interest: $558,000
- •15-year at 6.25%: $3,430/month · Total interest: $217,000
- •Difference: $769 more per month, but saves $341,000 in interest over the life of the loan
A common strategy: take the 30-year mortgage but make one extra principal payment per year. This can cut 5–7 years off your repayment and save $80,000–$120,000 in interest on a $400k loan — without the obligation of the higher payment.
When to Refinance
- 1.Use the break-even rule: divide closing costs by monthly savings to find break-even months. If you will be in the home longer than break-even, refinance.
- 2.Refinancing makes sense if rates have dropped by at least 0.75–1% from your current rate
- 3.Do not refinance if you are in the last 10 years of a 30-year mortgage — most of the interest is already paid
- 4.Consider a no-cost refinance where closing costs are rolled into the rate — it's a worse rate but zero upfront cost
- 5.Cash-out refinance: tapping equity to pay off high-interest debt can make sense if done once and the spending behavior that caused the debt is addressed
How to Pay Your Mortgage Off Faster
Even small additional principal payments have a compounding effect on payoff time. Adding $100/month to principal on a $400k 30-year mortgage can cut 4–5 years off repayment. Make sure your extra payments are designated to principal — not applied to future interest.