Amortization Calculator
Monthly payments, total interest, extra payment savings, in-school interest accrual, and deferment simulation. Add up to 5 loans.
How an Amortization Schedule Works
An amortization schedule is the complete, payment-by-payment breakdown of a loan. For each month it shows your starting balance, the portion of your payment that goes to interest, the portion that reduces principal, and your ending balance. On a typical fixed-rate loan the payment stays the same every month, but the split between interest and principal shifts dramatically over time—early payments are mostly interest, and later payments are mostly principal.
The monthly payment formula
For a fixed-rate loan, the level monthly payment is:
M = P × r(1+r)n / ((1+r)n − 1)
where P is the principal (loan amount), r is the monthly interest rate (annual rate ÷ 12), and n is the total number of payments (years × 12). Our calculator applies this formula per loan and per year, so you can see the cumulative interest you will pay if you make only the scheduled payments.
Principal vs. interest over time
In month one, interest is charged on the full balance, so most of your payment covers interest and only a little reduces principal. As the balance falls, the interest charged each month falls too, so a larger share of the same payment goes to principal. This "front-loaded interest" is why paying extra early in the loan saves the most money.
Reading this calculator's output
The table shows, for each year: the starting balance, total paid that year, how much was interest versus principal, and the ending balance. Use it to see exactly when you cross the point where principal payments exceed interest payments—that is the inflection point where the loan starts shrinking fast.
Subsidized vs. unsubsidized loans
With Direct Subsidized loans, the government pays the interest that accrues while you are in school (up to the subsidy period), so your balance does not grow. With Direct Unsubsidized loans, interest accrues from the day the loan is disbursed, even while you are in school. Enter your loans separately in this tool so the schedule reflects each loan's true starting balance.
Fixed vs. variable rates
Federal student loans have fixed rates set by law, so your schedule is predictable. Private loans may be variable; if yours is, model the schedule at the current rate but remember a rate increase will raise both your payment and total interest.
How extra payments change the schedule
Any extra amount applied to principal shortens the loan and cuts total interest, because every future month's interest is calculated on a smaller balance. This calculator lets you add an extra monthly or annual payment to see the new payoff date and interest savings.
Worked example
Illustrative: A $30,000 loan at 6% over 10 years has a scheduled payment near $333. Paying an extra $100/month cuts the term by about 2–3 years and saves meaningful interest. The exact figures depend on your rate and balance—use the tool for your numbers.
Frequently Asked Questions
Interest is charged on the current balance. At the start the balance is highest, so the interest portion is largest; as principal falls, the interest portion shrinks.
Usually no—your required payment stays the same, but the loan ends sooner and you pay less total interest. Some servicers let you request a re-amortized (lower) payment after a large principal reduction.
It depends on rates and risk. Paying off a 6–8% loan is a guaranteed return; investing may beat it over time but is not guaranteed. Many borrowers split the difference once they have an emergency fund.
The student loan interest deduction may apply up to the annual IRS limit, with income phase-outs. Confirm current limits at IRS.gov.
It occurs when a payment is too small to cover accrued interest, so the balance grows. Standard federal amortizing plans avoid this, but income-driven plans can pause interest in limited ways under the 2026 RAP framework—review your plan rules.
Sources: Federal Student Aid, IRS.gov. Educational use only; verify figures with your servicer.
Loan Term, Capitalization, and Refinancing
How the repayment term changes the schedule
Extending the term (say, from 10 to 25 years) lowers your monthly payment but dramatically increases total interest, because you pay on the balance for far longer. Shortening the term does the opposite: higher payments, far less interest. This calculator lets you compare terms directly to see the trade-off in dollars.
Interest capitalization
Capitalization is when unpaid accrued interest is added to your principal, so future interest is charged on a larger balance. Capitalization typically happens when a grace period or deferment ends, or when you leave an income-driven plan. Unsubsidized loans capitalize the in-school interest once you enter repayment. Paying the accrued interest before capitalization prevents the balance from snowballing.
Grace periods and in-school interest
Most federal loans have a six-month grace period after you leave school before payments start. For unsubsidized loans, interest keeps accruing during school and grace; for subsidized loans, the government covers it during the in-school and grace periods (up to limits). Enter the true starting balance—including any accrued interest—so your schedule is accurate.
Consolidation and refinancing effects
A Direct Consolidation Loan blends several loans into one with a weighted-average rate rounded up; it simplifies payments but usually extends the term and can raise total interest. Refinancing to a private loan may lower your rate but forfeits federal protections. Either way, re-run the amortization schedule afterward, because the new balance and rate change everything.
Reading the cumulative interest line
The single most useful number in any schedule is total interest paid over the life of the loan. Comparing that figure across terms or extra-payment amounts shows the real cost of every choice—often tens of thousands of dollars.
More Amortization Questions
Only if you cannot afford the higher payment. The longer term costs far more in interest. If cash flow is tight, an income-driven plan may be better than stretching a term.
Paying half your payment every two weeks yields 26 half-payments (13 full payments) a year—one extra payment annually—which trims the term and interest, similar to a recurring extra payment.
You fall behind on the schedule; late fees and delinquency can follow, and missed payments do not count toward IDR or PSLF forgiveness. Contact your servicer early to discuss options.
For federal fixed-rate loans, yes. For variable private loans, the schedule is a snapshot at the current rate and will change if the index rises.
Amortization in Your Bigger Financial Picture
Your loan schedule does not exist in isolation. Before sending extra money to principal, build a small emergency fund so a surprise expense doesn't push you back onto credit cards. Once that cushion exists, extra principal payments are one of the highest-confidence returns available, because you are eliminating a known interest rate.
When refinancing makes sense
If you hold private loans at a high rate and have stable income and strong credit, refinancing to a lower fixed rate can shrink both your payment and total interest. Keep federal loans federal unless you deliberately give up IDR, PSLF, and discharge protections. After any refi, re-run this amortization schedule with the new balance and rate.
Amortization and your credit
On-time payments are the largest factor in your credit score. A clean amortization history helps if you later apply for a mortgage. Setting up autopay also typically earns a small federal interest-rate reduction, which further lowers total interest.
Key Takeaways
- Early payments are mostly interest; extra principal paid early saves the most.
- The total-interest figure is the best single measure of a loan's true cost.
- Subsidized loans don't accrue interest during the subsidized period; unsubsidized loans do.
- Capitalization grows your balance—pay accrued interest before it capitalizes.
- Re-run the schedule after any refinance, consolidation, or extra-payment change.
Basic Amortization Calculator
Monthly payments, total interest, extra payment savings, in-school interest accrual, and deferment simulation. Add up to 5 loans.
Only affects in-school interest calculations. If you've already graduated or aren't using the "If Still In School" section above, all types produce the same amortization schedule.
🎓 If Still In School — Calculate Interest Accrual
⏸️ Simulate Deferment or Forbearance
View Full Amortization Schedule
Affects in-school interest only. No effect unless "If Still In School" is used above.