Amortization Calculator

How it works

How extra payments change amortization

An amortization schedule makes the effect of an extra payment visible in the remaining balance and later interest charges. Enter extras in the period when you expect to make them, rather than subtracting them from the starting balance. Compare the original payoff date with the revised date, and check any lender restrictions separately before treating the projection as your actual repayment schedule.

Loan & schedule: formula and assumptions

Payment = P × r / [1−(1+r)^−n], where r is the monthly rate.

Equal monthly payments amortize a fixed-rate loan. Extra payments reduce principal after the regular payment.

Calendar-based extra payments: formula and assumptions

Payment = principal / annuity present-value factor. Each month applies interest, scheduled payment, then extras.

Monthly, annual and dated one-time extras are combined. The final payment is capped at the debt owed. Compare the actual payoff and interest with an unchanged-payment baseline.

Worked example

Reference example currency: USD. These fixed examples do not change with your calculator preferences.

Using the Loan & schedule example:

Loan amount ($)

250000

Annual interest rate (%)

6.5

Term (years)

30

Extra monthly payment ($)

0

First payment month

2026-11-01

Payment = P × r / [1−(1+r)^−n], where r is the monthly rate.

Example result

These are illustrative inputs. Change the values to explore a different scenario.

What to keep in mind

Fees, variable rates, collateral requirements, and lender-specific payment conventions are not automatically included.

Formula references

• CFPB: understanding mortgages (opens in a new tab)
• Investor.gov: financial tools and calculators (opens in a new tab)

References explain the underlying methods; they do not imply endorsement or individual professional review of Finflo.

Common questions