On a $300,000 mortgage at 7% interest with a 30-year term, your first monthly payment is $1,996. Of that, $1,750 goes straight to the bank as interest. Only $246 reduces your loan balance. After 12 months of payments — $23,952 sent to your lender — your remaining balance is $297,055. You owe nearly as much as you started with. This is amortization: the interest share starts high because it is calculated on a larger balance. The CFPB explains how mortgage payments reduce the balance over time.
Why Interest Is Front-Loaded
Amortization front-loads interest because interest is calculated on the outstanding loan balance each month. In month one, the full $300,000 is at risk — so the bank charges 7% ÷ 12 = 0.583% on the full amount, which is $1,750. Your $1,996 payment covers that interest first; the remaining $246 reduces the principal. In month two, the balance is $299,754 — slightly less, so interest is slightly less ($1,748.50), and slightly more goes to principal ($247.50). The shift is gradual, compounding slowly in your favor over the life of the loan.
At payment 180, the $1,995.91 payment includes about $1,299.39 interest and $696.51 principal. Principal first exceeds interest at payment 242, approximately 20.2 years into this model, after about $352,918 in interest. The crossover depends strongly on rate and term.
Reading an Amortization Schedule
An amortization schedule is a month-by-month table showing, for every payment: the payment number, the total payment amount, the interest portion, the principal portion, and the remaining loan balance. Here is what the first few months look like on the $300,000 / 7% / 30-year example:
| Month | Payment | Interest | Principal | Balance |
|---|---|---|---|---|
| 1 | $1,995.91 | $1,750.00 | $245.91 | $299,754.09 |
| 2 | $1,995.91 | $1,748.57 | $247.34 | $299,506.75 |
| 12 | $1,995.91 | $1,733.75 | $262.15 | $296,952.57 |
| 60 | $1,995.91 | $1,649.32 | $346.58 | $282,394.77 |
| 180 | $1,995.91 | $1,299.39 | $696.51 | $222,056.60 |
| 360 | $1,995.91 | $11.58 | $1,984.33 | $0.00 |
The Total Cost of a 30-Year Mortgage
Using the unrounded mathematical payment, $300,000 at 7% over 360 months totals $718,526.69, including $418,526.69 interest. Real lenders round payments and may adjust the final installment. Fees and escrow costs are separate. See CFPB's loan guide for additional costs and terms.
How Extra Principal Payments Disrupt the Schedule
A $200 principal payment immediately after the first scheduled payment on this loan reduces modeled lifetime interest by about $1,413.89, with all later scheduled payments unchanged and a smaller final payment. The result is a full schedule calculation, not simply $200 multiplied by one year's interest rate.
Adding $200 to principal every month from the first payment gives payoff around month 275 instead of 360 and about $116,640 in modeled interest savings. This assumes no fees or prepayment penalties and immediate principal crediting. The basic loan form does not currently include this extra-payment scenario.
Always confirm with your lender that extra payments are applied to principal, not held as an advance on your next scheduled payment. Most servicers do this correctly when instructed, but some require explicit written direction each time.
Amortization on Auto Loans and Personal Loans
The same amortization math applies to auto loans and personal loans, just over shorter terms. A $35,000 auto loan at 8% for 72 months carries a monthly payment of $614. Over 72 payments, you pay $44,208 total — $9,208 in interest. Because the term is shorter, the front-loading effect is less severe than a 30-year mortgage, but the principle is identical. In month one, $233 of your $614 payment is interest. In month 36 (halfway), $143 is interest.
Interest-Only Loans: What Happens Without Amortization
Interest-only loans require no principal payments during the interest-only period — you pay only the interest charge each month, and the balance never decreases. On the $300,000 / 7% example, an interest-only payment is $1,750/month. At the end of a 10-year interest-only period, you still owe $300,000 and have paid $210,000 in interest with zero reduction in principal. When the loan converts to a fully amortizing payment, you now have 20 years to repay $300,000 — meaning your monthly payment jumps substantially. Interest-only structures can create cash-flow benefits in the short term but dramatically increase long-run cost.
Calculate Your Own Amortization Schedule
Our Loan Payment Calculator estimates the monthly payment for a fixed-rate loan. Enter the amount, annual interest rate, and term in months, then select View Amortization Schedule to see yearly totals for principal and interest and the balance at each year's end. It does not display individual monthly rows or include an extra-payment input. You can compare different loan terms, but ask your lender for a payment-by-payment schedule and confirmation of how additional principal payments would be applied.