Does the calculator show interest saved by adding extras?

Yes. The summary card reports total interest with and without extras and the months saved. The detailed schedule lets you confirm row by row.

Why does my last row look different?

Each month is rounded to whole cents, which can leave a tiny residual. The final period is adjusted so the ending balance lands on exactly $0.00.

Can I export the schedule?

Yes — there's a CSV download for the full month-by-month schedule, suitable for Excel, Numbers, or Google Sheets.

Amortization schedule with extra payments

An amortization schedule shows the principal/interest split for every month. Adding extras compresses the schedule and shifts the split toward principal sooner. Here's how to read it.

What an amortization schedule shows

For each month of the loan, the schedule records: beginning balance, scheduled payment, interest portion, principal portion, any extra principal applied, and the resulting ending balance. Without extras, the principal portion grows slowly over time as the interest charge on a shrinking balance falls. With extras, the shift toward principal accelerates immediately and the loan retires earlier.

How an extra payment changes a single row

A monthly extra is added to the principal portion of the row it's applied to. The ending balance drops by exactly that extra amount. From the next row onward, the interest charge is calculated against the lower balance — so every subsequent row records less interest and more principal, even though the scheduled payment is unchanged.

monthly_interest = beginning_balance * (annual_rate / 12)
scheduled_principal = scheduled_payment - monthly_interest
ending_balance = beginning_balance - scheduled_principal - extra_principal

Worked example

On a $320,000 loan at 6.5% over 30 years, the first scheduled payment is about $2,022 — roughly $1,733 in interest and $289 in principal. Add a $200 monthly extra: the same first payment now retires $489 of principal. By year 5, the difference compounds — the extra-payment schedule has roughly $11,000 less principal remaining than the baseline, and the loan retires several years earlier.

Reading the calculator output

Open the Amortization Calculator and enter loan amount, rate, and term.
Toggle to the "monthly" view to see every row, or the "yearly" view to see annual totals.
Add a monthly or one-time extra to see how the schedule compresses.
Use the CSV download to take the schedule into a spreadsheet for further analysis (year-over-year comparisons, scenario stacking, charts).

What to watch out for

The final period absorbs cents-rounding so the balance lands on exactly $0 — expect a small adjustment in the last row.
Extras are applied at the period scheduled. Servicer behavior can differ; confirm your bank applies extras to principal, not as future scheduled payments.
The schedule does not model rate changes (ARMs), recasts, or refinances — those reset the amortization to a new schedule.

Frequently asked

Does the calculator show interest saved by adding extras?: Yes. The summary card reports total interest with and without extras and the months saved. The detailed schedule lets you confirm row by row.
Why does my last row look different?: Each month is rounded to whole cents, which can leave a tiny residual. The final period is adjusted so the ending balance lands on exactly $0.00.
Can I export the schedule?: Yes — there's a CSV download for the full month-by-month schedule, suitable for Excel, Numbers, or Google Sheets.

Sources and references

Helpful consumer references used to explain assumptions on this page. These are educational pointers, not regulatory endorsement.

Internal — period-by-period engine — schedule walks the loan month by month with explicit interest, principal, and extras tracking
CFPB — understanding your mortgage statement — consumer reference for how monthly statements report principal vs. interest