How to read an amortization schedule

Generate a live schedule with the mortgage amortization calculator. This page is the legend for those columns.

The columns

• Payment #. 1 is the first due date you entered. A 30-year loan has 360 lines if you never prepay.
• Date. The assumed due date for that installment. Servicers may draft a few days earlier.
• P&I. The required principal and interest for that month. Extra principal is listed separately so you can see the contractual bill.
• Extra. Monthly habit plus any lump sum assigned to that payment number.
• Principal. Scheduled principal plus extra. This is the amount the balance falls.
• Interest. Remaining balance × monthly rate, rounded to cents.
• Balance. What is still owed after the payment. The last line is $0.00.

Year rollups

The bar above the table is that year’s mix of interest (copper) and principal (forest). Early years are copper-heavy. Click a year to open its monthly rows. If you added extras, later years disappear — that is the payoff coming in.

CSV export

“Export CSV” downloads every payment plus a header with loan amount, rate, term, extras, payoff date, and interest saved. The file is yours to open in a spreadsheet. Nothing is uploaded; the file is built in the browser. The last line of the CSV repeats that this is not lender advice.

When your lender’s schedule disagrees

Common causes: they included escrow, they used a different first-payment date, they started interest from the funding date (per diem interest at closing is not in this model), or they recast after a curtailment. Use their first-payment date and P&I, then compare year-one interest. A few dollars of drift over 360 months is rounding. Hundreds of dollars in month one is a different loan.

For the formula behind the rows, read how amortization works.