Mortgage Amortization Schedule — How Payments Break Down

What this calculator is

The Mortgage Calculator is an interactive tool inside GetCalcMaster. It’s designed to help you explore scenarios, understand formulas, and document assumptions.

Key features

• Early payments are mostly interest (typically)
• Principal share increases over time
• Extra payments can change the schedule significantly

Formula

Monthly payment (P&I):
M = P · r · (1+r)^n / ((1+r)^n − 1)
P = principal, r = monthly interest rate, n = number of payments

Quick examples

• P=$300,000, 6% APR, 30y → M ≈ $1,798.65 (principal+interest)
• Month 1 interest ≈ 300,000·0.06/12 = $1,500; principal ≈ $298.65
• Early payments are mostly interest; principal share grows over time

Verification tips

• Use the monthly rate r = APR/12 (as a decimal).
• Amortization schedules typically exclude taxes/insurance (escrow) unless added separately.
• Sanity check: longer terms lower payment but increase total interest.

Common mistakes

• Using APR as a percent (6) instead of decimal (0.06).
• Mixing payment frequency (monthly vs bi-weekly) without converting.
• Assuming “payment” includes taxes/insurance by default.

How to use it (quick steps)

1. Enter loan basics: home price (or loan amount), down payment, interest rate, and term.
2. Optionally expand advanced inputs (extra payments, PMI/escrow, ARM scenarios, and fees).
3. Review monthly payment, payoff timeline, total interest, and the amortization schedule.
4. Export your scenario for record‑keeping, then verify details with lender disclosures and official documents.

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FAQ

Tip: For reproducible work, save your inputs and reasoning in Notebook.