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Finanza & Denaro5 min•2026-10-29•Compute-Hub Finance Editorial
How Loan Amortization Works: Principal vs. Interest Explained
Understand why early payments barely touch principal and how amortization schedules calculate monthly payments.
Key Takeaways
- Amortization equalizes monthly payments while shifting the proportion from interest to principal over time.
- Early monthly payments are overwhelmingly absorbed by interest charges.
- Every extra dollar applied directly to principal shortens your loan term and reduces future interest charges.
- Fixed-rate mortgages shield borrowers from market rate increases, providing predictable payment schedules.
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The Amortization Payment Formula
Lenders calculate fixed monthly payments using standard annuity formulas that account for total loan principal, monthly interest rate, and total monthly periods.
Mathematical Formula:M = P × [ i(1 + i)^n ] / [ (1 + i)^n – 1 ]
💡 Practical Real-World Example:A $250,000 loan at 6% annual interest for 30 years yields a monthly principal and interest payment of $1,498.88.
Why Early Payments are Interest-Heavy
Because interest is computed monthly based on the outstanding principal balance, month 1 interest is highest ($1,250 on $250k). Only $248.88 reduces principal in month 1. By year 25, the ratio flips completely.
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Frequently Asked Questions
FAQ: How Loan Amortization Works: Principal vs. Interest Explained
What is negative amortization?
Negative amortization happens when monthly payments do not cover accrued interest, causing outstanding loan balance to grow.
Where can I view an exact amortization schedule?
Compute-Hub’s Amortization Calculator generates full annual and monthly balance breakdowns with interactive charts.