Investing metrics
Amortization
The schedule by which a loan is paid off over time, with each payment split between interest and principal.
Glossary
Investing metrics
Primary references on this page:
Amortization is the process of paying off a loan gradually through regular payments. Each payment is split between interest and principal, but the mix shifts over the life of the loan: early payments are mostly interest, and later ones are mostly principal. An amortization schedule lays out that split payment by payment.
The principal portion of every payment is what builds your equity — sometimes called the “loan paydown” return of owning a rental. A standard 30-year fixed loan fully amortizes to a zero balance by the end of its term; some loans instead are interest-only or end in a balloon payment, meaning they amortize slowly or not at all. (The same word is also used in accounting for spreading the cost of an intangible asset over time.)
A level-payment schedule changes its internal mix
For a fully amortizing fixed-rate loan, the periodic principal-and-interest payment is P × r ÷ (1 − (1 + r)^−n), where P is opening principal, r is the periodic interest rate, and n is the remaining number of payments. Each period’s interest is opening balance × r; principal is payment minus interest; and closing balance is opening balance minus principal. Contract rounding, timing, fees, escrow, late activity, and servicing rules can make an actual statement differ.
For a $300,000 loan at 6.00% nominal annual interest with 360 monthly payments, the calculated monthly principal-and-interest payment is $1,798.65. First-month interest is $1,500.00, principal is $298.65, and the unrounded remaining balance is $299,701.35. The next payment applies slightly less to interest because its opening balance is lower.
Use the schedule for debt questions, not total-return claims
Identical payments do not create identical principal reduction at different rates or points in the schedule. A sale or refinance before maturity depends on the balance at that date. Refinancing creates a new rate, term, costs, and schedule; additional principal can change the payoff path but must be applied according to the loan agreement.
Loan amortization does not include taxes, insurance, operating performance, appreciation, sale proceeds, or taxes on the investment. It also differs from accounting amortization, which allocates the cost of certain intangible assets. Use a current servicer statement or payoff quote for an actual payoff decision.