How Amortization Works
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Amortization repays a balance through scheduled payments; interest is charged on the outstanding balance and the remainder of each payment reduces principal.
The repeating sequence
Start with opening balance. Multiply it by the periodic note rate to calculate interest. Subtract interest from the payment to find principal. Subtract principal and any accepted extra principal from the balance. Repeat until the final payment clears the debt.
Run the numbers in the Amortization Calculator with the same assumptions used in this guide.
Why the split changes
On a level-payment fixed-rate loan, the opening balance is highest at the beginning, so early interest is larger. As principal falls, interest generally falls and more of the same payment reduces principal.
Read each column
Payment date identifies timing; payment is scheduled principal plus interest; extra principal should have its own column; closing balance becomes the next opening balance. Escrow is not principal or interest.
Use milestones
Compare the first payment, one-year balance, midpoint, and final payment. Confirm total principal equals original principal and the last balance is zero. Annual summaries help navigation but should reconcile with detailed rows.
Fixed-rate boundary
A standard schedule cannot predict ARM rate resets, missed payments, daily-interest servicing, fees, or recasts unless modeled. Use it to understand the stated scenario, not to replace the contract.
Frequently asked questions
Does amortization mean the payment changes?
Not on a standard level-payment fixed-rate schedule, although the principal-interest split changes.
Is escrow amortized?
No. It is collected for separate property costs.
Why can the last payment differ?
It is adjusted for the remaining principal and rounding.
Can I use the schedule for an auto loan?
Yes if the loan follows the same fixed-rate periodic method; contract-specific daily interest may differ.
From loan balance to housing exit equity
The remaining principal in this schedule reduces estimated sale proceeds; it is not the same as the sum of past mortgage payments. To compare those proceeds with renting, sale costs and cash invested on both paths, use the Rent vs Buy Calculator and read how its crossover is defined.
Sources
- CFPB amortization explanation: https://www.consumerfinance.gov/ask-cfpb/what-is-amortization-and-how-could-it-affect-my-auto-loan-en-771/
- CFPB interest rate vs APR: https://www.consumerfinance.gov/ask-cfpb/what-is-the-difference-between-a-mortgage-interest-rate-and-an-apr-en-135/
- CFPB mortgage servicer rules: https://www.consumerfinance.gov/consumer-tools/mortgages/your-mortgage-servicer-must-comply-with-federal-rules/
Source research refreshed September 21, 2026. The calculation, source, and content checks were refreshed on September 21, 2026. This page provides educational estimates, not lending, legal, tax, or financial advice.
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