Tabla de Amortización de Préstamo

What an amortization schedule shows that a payment figure hides

A loan calculator can tell you a single number: your monthly payment. An amortization schedule tells the rest of the story — exactly how that fixed payment is divided between interest and principal in every single month, and how your balance falls from the full loan amount down to zero. This tool generates that entire row-by-row table, draws a chart of the principal-to-interest ratio over the life of the loan, and lets you export the whole thing as a CSV. The payment number is the headline; the schedule is where you actually understand the loan.

How each row is built

The schedule is computed one month at a time, in sequence. For each payment the tool does three things:

1. Interest = current balance × monthly rate. The monthly rate is the annual rate divided by 12 (and by 100). This is the cost of borrowing the outstanding balance for that one month.
2. Principal = fixed payment − interest. Whatever is left of your payment after covering the interest actually reduces what you owe.
3. New balance = old balance − principal. Carry that forward and repeat for the next month.

Because the payment stays constant but the balance shrinks every month, the interest portion falls month after month and the principal portion grows — the two trade places gradually. The stacked bar chart in the tool makes this visible at a glance: a tall red (interest) base at the left that shrinks into a tall blue (principal) bar at the right.

A worked example with the tool's defaults

Take the default $200,000 loan at 6.5% over 30 years (360 payments). The monthly rate is 6.5 ÷ 100 ÷ 12 ≈ 0.005417, and the fixed payment works out to about $1,264.14. Now look at where that payment goes:

In month one, 86% of your payment is pure interest and only about $181 chips away at the debt. Notice the halfway point: after 15 years of payments the balance is still around $135,000 — far more than half — because the early years were front-loaded with interest. Over the full term you pay roughly $455,000, of which about $255,000 is interest: more than the house cost to borrow.

Why the balance falls so slowly at first

This "front-loading" is the most important thing the schedule reveals, and it's not a trick by the lender — it's arithmetic. Interest is charged on the balance, and early on the balance is huge, so interest eats most of the payment. As principal slowly accumulates, the balance drops, the interest charge drops with it, and more of each payment attacks the principal. The result is a curve, not a straight line: equity builds slowly, then accelerates. This is precisely why selling or refinancing in the first few years leaves you with little equity, and why the schedule, not the monthly figure, is what you should study before signing.

The power of paying extra — and why timing matters

Any dollar you pay above the scheduled amount goes straight to principal, and because future interest is charged on a now-smaller balance, that one extra dollar erases all the interest it would otherwise have accrued for the rest of the term. The effect compounds, and it is dramatically larger early in the loan than late. On the example above, an extra $200 a month from day one cuts roughly eight years off the term and saves tens of thousands in interest — money that simply never gets charged because the balance reaches zero sooner. The same $200 applied in year 25 saves almost nothing, because there's barely any interest left to avoid. To model this, you can shorten the term in the tool, or read the schedule to see how much faster the balance would fall.

Reading the table and exporting it

The tool shows the first 12 rows by default with a button to expand the full schedule. Each row lists the payment number, calendar date (driven by the start date you set), the principal and interest split, and the running balance. The Export CSV button downloads every row — all 360 for a 30-year loan — so you can open it in a spreadsheet, build your own charts, or compare two loans column by column.

What the schedule does not include

• Taxes, insurance, PMI, and HOA dues. The figures are principal and interest only. A real mortgage payment often bundles property tax and insurance into escrow, which can add hundreds of dollars a month.
• Variable rates. The math assumes a fixed rate for the whole term; an adjustable-rate loan would recompute the payment at each reset.
• Fees and points. Up-front closing costs change the true cost of borrowing but not the monthly principal-and-interest split shown here.

Privacy

Every row is computed in your browser from the four inputs you enter, and the CSV is generated locally on your device. Nothing is sent to a server, so you can model as many scenarios as you like — comparing terms, rates, and start dates — completely privately.