Loans and Amortization
Every loan payment splits between interest and principal, and that split moves every month. Step through an amortization schedule below and see why an early extra payment is worth so much more than a late one.
Every fixed loan payment looks identical on the statement, month after month. Underneath, the split between what pays down what you borrowed and what pays the lender for lending it to you is quietly moving the entire time — and it starts far more lopsided than most borrowers expect.
Every payment splits between interest and principal
Amortization is the schedule that splits a fixed loan payment into two pieces every month: interest, which is the lender's fee on whatever balance is still outstanding, and principal, which actually reduces what you owe. The payment amount never changes — only the ratio between the two pieces does.
Early payments are mostly interest
Interest is calculated on the remaining balance, and early in a loan the remaining balance is close to the full amount borrowed — so early payments are mostly interest, with only a small sliver going toward principal. Step through the schedule below month by month and watch that ratio flip as the balance shrinks.
Interest
$100
Principal
$287
Balance left
$19,713
A one-time $1,000 extra payment
Applied in month 1, it saves $334 in interest over the life of the loan. Applied in month 55, near the end, it saves only $21. The same dollar amount, the same loan — the only difference is how many months of interest it had left to prevent.
Why an extra payment early saves more than one late
An extra principal payment works by shrinking the balance interest gets calculated on, for every remaining month of the loan. Made early, it prevents interest across nearly the whole remaining term. Made near the end, there are only a handful of months left for it to matter — the same dollar amount, doing far less work.
Key takeaways
- Amortization splits a fixed loan payment into interest, calculated on the remaining balance, and principal, which actually pays down the loan.
- Because interest is calculated on the outstanding balance, early payments on any loan are mostly interest and only slightly reduce what's owed.
- That ratio flips as the loan matures — later payments are mostly principal, since the remaining balance is smaller.
- An extra payment made early prevents interest across nearly the whole remaining term; the same amount made late has far fewer months left to save on.