Mortgage Amortization Calculator

Worked example

Example: a $300,000 loan at 6% for 30 years gives a fixed monthly payment near $1,799 with early payments mostly interest and later payments mostly principal.

When to use this

• Reviewing year-one interest vs principal on a new purchase loan.
• Comparing 15-year vs 30-year amortization interest totals.
• Testing extra principal effects on payoff date.
• Explaining early-payment interest to first-time buyers.
• Checking remaining interest before a refinance decision.

Common examples

• $350,000 at 6.75% 30-year → ~$2,270 P&I; year-one interest-heavy.
• Same loan 15-year → higher payment, far less total interest.
• +$200/month extra principal → payoff date moves in years earlier.
• Refinance remaining balance at new rate → rebuild amortization.
• Biweekly plan → enter adjusted payment schedule to compare interest.

Common mistakes

• Reading P&I rows as if they already include tax and insurance.
• Using list price instead of loan amount after down payment.
• Skipping the schedule and only comparing headline monthly payment.
• Assuming biweekly payments are modeled without changing inputs.
• Ignoring that rate changes require a new amortization run.

How it works

Builds a full amortization schedule from loan amount, annual interest rate, and term. Shows monthly payment plus principal and interest split for each period.

Limitations

Schedule assumes fixed rate and on-time payments. Extra principal, escrow changes, and ARM adjustments are not modeled.

Privacy and file handling

Your data stays on your device and is not uploaded.

Formula or method

Monthly payment uses standard fixed-rate amortization; each period applies interest to the remaining balance and allocates the remainder to principal.

Important notice

Results are estimates for educational purposes and are not financial advice. Actual lender schedules may differ slightly. Consult a qualified financial professional for personal guidance.