Financial Modeling
How Amortization Shifts Interest vs Principal Across a 30-Year Mortgage
Understand why early monthly mortgage payments go mostly toward interest—and how even small extra principal payments cut years off your loan.
November 14, 2026By PureCalculator Editorial Lab5 views1 min read
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Why Early Payments Skew Toward Interest
In a fixed-rate amortized loan, your combined monthly principal-and-interest payment remains constant, while the internal split shifts each month. Interest is always computed against the remaining principal balance at the start of the billing cycle.
Testing the Impact of Extra Principal
Open the Mortgage Calculator or launch 15-Year vs 30-Year Scenario Compare to see how adding an extra monthly payment directly reduces the principal base and eliminates downstream compounding interest.
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