Real Estate Glossary

What is Amortization? Definition, Formula & Examples

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Definition

Amortization is the process of paying off a loan through scheduled, fixed payments over time, where each payment covers both interest and a portion of the principal balance. Early in a loan's life, most of each payment goes toward interest. Over time, the principal portion grows while the interest portion shrinks — this is the amortization schedule. For real estate investors, understanding amortization helps quantify the equity buildup component of their total return.

The Amortization Formula

Monthly Payment = P × [r(1+r)^n] / [(1+r)^n − 1]

Variables explained:

P = principal loan amount (purchase price minus down payment). r = monthly interest rate (annual rate / 12). n = total number of monthly payments (loan term in years × 12). This formula calculates the fixed monthly payment that fully retires the loan at the end of the term.

Amortization Example with Real Numbers

You borrow $240,000 at 7% for 30 years. Monthly rate = 0.07/12 = 0.5833%. Monthly payment = $240,000 × [0.005833 × (1.005833)^360] / [(1.005833)^360 − 1] = $1,597. In month 1, $1,400 goes to interest and only $197 to principal. By year 20, approximately $780 goes to principal and $817 to interest on the same payment.

Why Amortization Matters for Investors

Amortization creates forced savings — every mortgage payment builds equity even without appreciation. Over a 30-year loan on a $240,000 mortgage, you pay roughly $575,000 total ($335,000 in interest). This is why investors often prefer shorter loan terms or making extra principal payments to reduce total interest paid. Amortization schedules also help investors project equity at any future point for refinancing decisions.

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Frequently Asked Questions

What is a 30-year amortization schedule?

A schedule showing all 360 monthly payments, with each payment split between interest and principal. In the first year, roughly 80–85% of each payment is interest. By year 30, almost all of each payment is principal.

How does making extra principal payments affect amortization?

Extra principal payments directly reduce the outstanding balance, which reduces future interest charges and shortens the loan term. On a $240,000 30-year loan at 7%, an extra $200/month saves over $80,000 in interest and cuts the payoff by 7+ years.

Is amortization the same as depreciation?

No. Amortization applies to loan payoff over time. Depreciation (in real estate) refers to the IRS allowance to deduct the cost of a building over 27.5 years as a paper expense. Different concepts, both important for investors.

What is negative amortization?

Negative amortization occurs when loan payments are too small to cover the interest, so the unpaid interest is added to the principal balance. The loan grows rather than shrinks. This occurred with some risky mortgage products before 2008.

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