Example 1 — Monthly extra payment
- Principal: 300,000
- Rate 6.5%, term 25 years
- Extra: +300/mo.
6 yr 5 mo. earlier
Interest −91,174.74
An extra 300 a month shortens a 25-year loan by more than 6 years and cuts interest by about 30%.
Loan amortization schedule with extra payments
See the full amortization schedule for a fixed-rate loan and check how monthly, yearly, or one-time extra payments shorten the term and cut interest.
Enter the loan amount, annual interest rate, and term — the calculator builds a full month-by-month annuity amortization schedule and compares it with an accelerated version. Add a recurring extra payment (monthly or yearly) or a one-time lump sum on a chosen payment. This is an educational fixed-rate model — no early-repayment fees or rate changes. Amounts follow the currency in the header.
Result
Enter data and click Calculate.
Payment schedule
How results are calculated
Base payment = the annuity payment from the loan amount, annual rate, and term — fixed for the whole term until you add extra payments.
Base schedule simulates the payoff month by month with no extras: each payment splits into interest (balance × monthly rate) and principal (payment − interest).
Schedule with extras adds every matching extra payment to the principal: monthly — every month, yearly — in the month you choose, one-time — on the payment number you pick. An extra never exceeds the remaining balance; the simulation ends once the balance reaches zero.
Interest saved and time saved are the difference in total interest and number of payments between the base scenario and the one with extras.
How to use the calculator
- Enter the loan amount, annual interest rate (%), and term in years.
- Optionally set the first payment date — it sets the schedule dates and, with a yearly extra, also which calendar month receives that payment.
- Open "Extra payments (optional)" to add a recurring monthly extra, a recurring yearly extra (pick the month), or a one-time lump sum on a specific payment.
- Check the result cards: the payment, base and accelerated total interest, interest saved, and the new payoff date.
- Switch the schedule view between monthly and yearly, and between the base and with-extras scenario.
- Export the currently displayed schedule to CSV if you want to analyze it further in a spreadsheet.
Usage examples
Example 2 — Yearly extra (bonus)
- Principal: 400,000
- Rate 7%, term 30 years
- First payment date: Jan 1, 2026
- Extra: 6,000/yr in December
10 yr 6 mo. earlier
Interest −222,094.77
A yearly December bonus of 6,000 (with a January start) shortens a 30-year loan by more than 10 years.
Example 3 — One-time lump sum
- Principal: 200,000
- Rate 5.5%, term 20 years
- Lump sum: 15,000 on payment #24
2 yr 3 mo. earlier
Interest −22,880.72
A lump sum two years into the loan immediately lowers the principal and shortens the rest of the schedule.
FAQ
How is the amortization schedule with extra payments calculated?
First we compute the fixed annuity payment from the loan amount, interest rate, and term. Then we simulate the payoff month by month: each payment splits into interest (balance × monthly rate) and principal. Extra payments add to the principal portion and speed up the balance reaching zero.
What is the difference between recurring and one-time extra payments?
A monthly extra is added to every payment, a yearly extra is added once a year in a month you choose (e.g. from a bonus), and a lump sum applies only to the payment number you pick. You can combine all three and see the total effect.
What happens if an extra payment exceeds the remaining principal?
The calculator caps the extra at the remaining balance for that month — the loan can never go below zero. The final row in the schedule closes the balance out to exactly zero.
Does an extra payment shorten the term or lower the payment?
This calculator assumes the payment stays fixed and extra payments shorten the term — the most common arrangement with lenders. Some contracts instead let you lower the payment at the same term; check your loan agreement.
Why does the base payment stay the same despite extra payments?
The annuity payment depends only on the loan amount, rate, and term — extra payments don’t change its size, they only accelerate principal repayment and shorten the real duration of the loan.
What do the balance chart and cumulative interest chart show?
The balance chart compares how quickly the principal shrinks in the base scenario versus with extra payments. The interest chart shows the running total of interest paid over time — the sooner the "with extras" line pulls below the base line, the bigger the savings.
Can I export the schedule to a spreadsheet?
Yes — the "Export CSV" button downloads the currently displayed view (monthly or yearly, base or with extras) as a CSV file you can open in Excel or Google Sheets.
Where does the currency in the results and table come from?
Calcboxer keeps one currency for the whole page — changing it in the header updates the amounts shown in the result cards, the schedule table, and the charts.