Payment Calculator

How it works

Choosing a payment or a payoff target

Use the scheduled-loan mode when the amount, rate, and term are known. Use fixed-payment payoff when you want to see what a chosen payment does to an existing balance. Check whether that payment covers accruing interest and reduces principal. A payment that looks manageable today may extend repayment considerably, so review the payoff duration as well as the installment amount.

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.

Fixed-payment payoff: formula and assumptions

Payoff months = −ln(1−Pr/payment) / ln(1+r).

The monthly payment must exceed the interest due. The final installment is reduced to the remaining balance.

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

Assumes a fixed rate and no new borrowing or late fees.

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