I priced a $10,000 loan at 6% for one year, first payment 15 Jan 2026. The monthly payment came out to $860.66. I added the twelve payments and the balance was not zero. Four cents were still sitting there.
The next row is 15 Jan 2027. The payment is $0.04. The interest is $0.00. The balance is $0.00. Total interest on the year is $327.96.
That last row is rounding. I wanted it on the page, in the CSV, and in the spreadsheet, as the text 0.04, because a float that prints 860.659 is how a ten-thousand-dollar loan starts lying to you.
The page is Amortization Schedule.
Twelve payments left four cents
Payment 12 falls on 15 Dec 2026. The payment is still $860.66. Interest that month is $4.28. Principal is $856.38. The balance after that row is $0.04.
A calculator that folds those four cents into December will show a last payment of $860.70 and a balance of zero, and the twelve payment amounts will no longer match. A calculator that drops the four cents will show a balance of zero while the payments add up to $10,327.92 of principal and interest against a loan that owed $10,328.00. Four cents, gone, and nobody can say where.
I kept them as their own row. The sum of every payment, plus every extra, equals the principal plus the interest. On this loan that means the payments add to $10,327.96, which is $10,000 plus $327.96. The balance column ends at 0.00 and never goes below it.
After twelve payments of $860.66, four cents are left. 15 Jan 2027 pays $0.04 and the balance is zero.
The first month is fifty dollars
6% of $10,000 for a twelfth of a year is $50 exactly. The first row, 15 Jan 2026, shows interest $50.00, principal $810.66, balance $9,189.34.
The second month is where the cents start. The balance is $9,189.34. One twelfth of 6% of that is $45.9467, and half-up rounding makes it $45.95. Principal that month is $814.71. Balance is $8,374.63.
I round interest half up to the cent, every period, from the balance at the start of that period. The rule is balance times the annual rate, divided by the number of periods in a year, then half up. Monthly, that divisor is 12. Every 14 days, the divisor is 26. I am not citing a statute for the half-up step. It is the rule this page uses, and the files follow it.
| Month | Date | Payment | Interest | Principal | Balance |
|---|---|---|---|---|---|
| 1 | 15 Jan 2026 | 860.66 | 50.00 | 810.66 | 9189.34 |
| 2 | 15 Feb 2026 | 860.66 | 45.95 | 814.71 | 8374.63 |
| 12 | 15 Dec 2026 | 860.66 | 4.28 | 856.38 | 0.04 |
| 13 | 15 Jan 2027 | 0.04 | 0.00 | 0.04 | 0.00 |
The middle months follow the same rule. By November the interest is $8.54 and the balance is $856.42. December takes that down to four cents. January pays the four cents.
How $860.66 got picked
The payment is the ordinary annuity on $10,000 at 6% for 12 months. Unrounded, it is about $860.664. Rounded to the cent, the stored payment is $860.66. That same $860.66 is what the CSV writes, and what the spreadsheet writes, in the first data row.
A zero rate skips the annuity. $1,000 at 0% for the same year is $83.33 a month, twelve times, and a thirteenth payment of $0.04 on 15 Jan 2027. Interest is $0.00 on every row. Twelve times $83.33 is $999.96. The last four cents bring the paid total to $1,000.00. Same leftover-row rule as the 6% loan. I did not stuff the four cents into payment 12 and call it $83.37, because then the scheduled payment would be a lie for eleven months and a different number once.
A hundred dollars on every row
The sample on the page adds $100 to each monthly payment. The scheduled payment stays $860.66. The extra column is $100.00. Interest for the year falls from $327.96 to $295.77. That is $32.19 less interest. The loan ends on 15 Nov 2026, in 11 payments, and the last of those is $689.17, because the balance does not need a full payment anymore.
The status line says the extras save $32.19. That number is the no-extra schedule minus this one, on the same rate, the same term, and the same first date. Change the rate and the saved figure changes with it. I do not compare a monthly plan to an every-14-days plan and call the difference "saved." Those are two different calendars.
The extra does not touch the first interest
The first month's interest is still $50.00 when you add $100. The extra has not reduced the balance yet. Interest is charged on the balance at the start of the period. Then the payment and the extra come off.
That order matters if you are checking the sheet against a lender statement. If their statement takes the extra off before the interest, the first month will not be $50.00, and you should believe the note, not this page. I say that on the page because a partial payment is not a right you can assume. The CFPB's Closing Disclosure explainer, last modified on the bureau's site on 10 Oct 2023, says a lender can refuse a partial payment, hold it, or charge a late fee until you make up the difference.
An extra larger than what you owe gets cut down. A $100 loan at 0%, with an extra of $1,000 typed in, is one row. The scheduled piece is $8.33. The extra piece is $91.67. Together they are $100.00. The balance is zero. The extra column is not $1,000.
Five hundred dollars on 15 Mar
A dated extra lands on the first payment on or after that date. Put $500 on 15 Mar 2026 and the March row's extra column is $500.00. The March interest is still computed on the February balance, before that $500 comes off.
A date after the payoff is listed and not applied. On this one-year loan, $500 dated 1 Jan 2030 never finds a row. The page says so, instead of pretending the money reduced a balance that was already zero.
One dated extra is all the form holds. If you have three, download the file, and add the other two in your own sheet. I would rather say that than invent a second and third box and then drop one on the way into the file.
The anniversary is the same month and day
Once a year, an extra can land on the payment whose month and day match the first payment, and whose date is after the start. On a 30-year run of the same $10,000 at 6%, starting 15 Jan 2026, a $500 anniversary extra shows up on 15 Jan 2027 as $500.00 in the extra column. It does not show up on the first payment. The first payment is the start, not an anniversary.
On the one-year loan, the anniversary falls when only a few cents are left, so the extra is cut to what is left. The balance still ends at zero. I checked that on the 30-year loan when I wanted to see the full $500, and on the one-year loan when I wanted to see the cap.
31 Jan does not invent a 31 Feb. 2026 is not a leap year, so the next monthly date is 28 Feb 2026. March keeps the 31st. The months are counted from the original start date, not by chaining "add one month" off the previous row, which is how 31 Jan becomes 2 Mar or 3 Mar in a library that overflows.
Every 14 days is half the payment
Switch the same loan to every 14 days and the payment becomes $430.33. That is half of $860.66, not a new annuity on 26 periods. The first date is still 15 Jan 2026. The second is 29 Jan 2026, fourteen days later.
The first period's interest is $23.08. It is not $50.00. If a "biweekly" calculator still shows $50.00 on the first line, it is still thinking in months and then dropping in a thirteenth payment somewhere. This page charges interest 26 times a year, at one twenty-sixth of the annual rate, half up to the cent.
This sample does not run all 26. It pays off on 3 Dec 2026, after 24 payments. Total interest is $290.01. The last payment is $392.42, short of $430.33, because the balance ran out. The status line does not call the gap versus the monthly plan "saved." There was no extra payment on this run. The calendar itself is different.
A year of that rhythm is 26 half payments, which is the cash of 13 monthly payments. That is the point of the 14-day plan. The sample just happens to finish in December, before the 26th one.
The cells are the cents, as text
The CSV and the XLSX write 860.66 and 0.04. They do not write 860.659. I opened the spreadsheet XML and looked for those strings. The cells are inline text, not Excel formulas, and not floating-point numbers that a later open might round differently.
A live formula would recompute interest with Excel's own rounding, and the last row would drift from the table you already looked at. I would rather the file match the screen. If you want formulas, you have the columns: date, payment, extra, interest, principal, balance. You can wrap them. The values you downloaded are the ones the page showed.
The table on the phone scrolls. Twelve hundred rows is the cap. Past that, the page says the balance is still above zero and it stops. I am not going to spin a progress bar for a calculation that finishes in the click. The loan amount stops at $10,000,000. Years on the saved setup run from 1 to 40. The rate runs from 0 to 30.
A Closing Disclosure is a different piece of paper
This page is principal and interest. The CFPB explainer says principal and interest usually make up the main part of the monthly payment, and the total is typically more, because taxes, insurance, and mortgage insurance can sit on top. None of those are in the payment here. Escrow is not here. A rate lock is not here.
The form the bureau is describing is the lender's Closing Disclosure. You get it before closing, and it is the lender's numbers. This page will not print one. The APR on that form is a different measure of cost than the note rate this table multiplies. The bureau's TIP is the interest over the life of the loan. The interest total on this page is that idea for principal and interest only. It is not the TIP from a disclosure you have not uploaded, because you cannot upload one here.
A prepayment penalty, if the note has one, is not subtracted. A balloon, in the bureau's words, is a final payment much larger than the others. The $0.04 row is the opposite of that. If a payment ever fails to cover the interest, the balance rises, the principal column stays 0, and the page says the balance went up. The bureau calls that negative amortization, and it says most loans do not have it.
The dollars stay in the tab
The loan amount and the extras are not written to the saved setup. Close the tab and they are gone. What this browser does keep, under softery.amortization-extra-payments.settings, is monthly or every 14 days, the years, the rate, and the first payment date. Clear saved setup removes that.
The share link carries those four knobs. It does not carry $10,000, and it does not carry the $100. The preview is the URL itself, on the page, before you copy it. A ?v= cache buster does not replace a setup you already saved.
Mixpanel and Google Analytics load with Softery.io. They see that someone opened the tool. A download reports a size band and a row count. They do not get the loan amount.
A percent question, like a down payment, belongs on the Percentage Calculator. What a dollar was worth in another month belongs on the Inflation Calculator. This schedule does not adjust a 2015 balance into 2026 dollars.
Open the sample before you type your own
- Open the amortization schedule and click Use the sample.
- Read the status line. Payment $860.66. Interest $295.77. Paid off 2026-11-15. Extras save $32.19.
- Find $50.00 in the first interest cell, and $100.00 in the extra column.
- Download the CSV. The first payment cell is
860.66. - Switch How often to Every 14 days, clear the extra back to 0, and build again. The first interest should be $23.08, and the payoff should be 3 Dec 2026.
- If you copy the setup link, read it. Frequency, years, rate, and the first date. No loan amount.
Then put your own numbers in. If the note disagrees with this table, the note wins. This page is a schedule you can check, export, and throw away.
Last updated: September 22, 2026 | Reading time: 11 minutes
Written by Softery.io, which kept four cents in their own row instead of folding them into December.