Finance
Extra Loan Payment & Interest Savings Calculator
Compare regular payments with extra monthly or lump-sum principal payments to see interest savings and months saved. Nothing you enter leaves your browser.
Enter your values, then calculate.
Calculation method
A transparent estimate.
Every adjustable assumption stays visible, so you can understand what drives the result and tailor it to your situation.
Payment ≈ P × r / (1 − (1 + r)^−n), or P / n at 0% interest; P = remaining principal, n = months, r = annual interest rate (%) / 1200. Monthly interest = balance × r; principal paid = payment − interest. Interest saved = original total interest − total interest with extra payments.What this estimate assumes
- Uses USD, a fixed nominal annual interest rate, and monthly payments at the end of each month. Enter the interest rate rather than APR, which may include fees.
- Interest is rounded to cents monthly. Estimated payments use the smallest whole-cent amount that repays the balance within the selected term; the final payment is capped at the amount owed.
- Supports 1–600 months and annual interest rates from 0% to 100%. Taxes, insurance, variable rates, daily interest, and prepayment penalties are excluded.
- The regular payment is estimated from the remaining balance and term. A lump sum reduces principal immediately, before interest accrues, and is capped at the remaining balance.
- Extra monthly payments start with month 1 and go toward principal after interest. The regular payment stays fixed; the loan is not recast. Confirm how your lender applies extra payments.
Research sources
What this tool does
About the Extra Loan Payment & Interest Savings Calculator
Compare regular payments with extra monthly or lump-sum principal payments to see interest savings and months saved. It is a planning aid for comparing scenarios; it is not financial, tax, lending, or investment advice.
The calculation uses remaining loan balance, annual interest rate (not apr), remaining loan term, extra monthly principal payment, and immediate lump-sum principal payment.
How to use it
- Review the starting values for remaining loan balance, annual interest rate (not apr), remaining loan term and replace them with your own.
- Choose any available units or assumptions, then select “Calculate interest savings.”
- Read the labeled result, compare another scenario if needed, and copy the output for your notes.
Practical example
Start with a known input
The workbench starts with a complete scenario: Remaining loan balance: 25000 $ Annual interest rate (not APR): 7.5 % Remaining loan term: 60 months Extra monthly principal payment: 100 $ Change one assumption at a time to see how it affects the result.
What to know about the result
- Results are estimates based only on the supplied values. Rounding, fees, local rules, and real-world conditions may change the final outcome.
Common questions
Using the Extra Loan Payment & Interest Savings Calculator
Is the Extra Loan Payment & Interest Savings Calculator free to use?
Yes. FormatCalc's Extra Loan Payment & Interest Savings Calculator is free to use with no account required.
Is my data private when I use the Extra Loan Payment & Interest Savings Calculator?
Yes. This tool processes your input locally in your browser. FormatCalc does not upload or store what you enter.
How do I use the Extra Loan Payment & Interest Savings Calculator?
Enter your values, select any units, and choose Calculate interest savings. You can then copy the result.
How is the Extra Loan Payment & Interest Savings Calculator calculated?
It uses Payment ≈ P × r / (1 − (1 + r)^−n), or P / n at 0% interest; P = remaining principal, n = months, r = annual interest rate (%) / 1200. Monthly interest = balance × r; principal paid = payment − interest. Interest saved = original total interest − total interest with extra payments.. The result is a planning estimate based on the values and assumptions shown on this page.