CalcKitStudent Loan Calculator
Your student loan
Any extra amount you pay each month goes straight to the principal, which cuts your total interest and shortens the loan. Leave it at $0 to see the standard payment.
Example: $30,000 borrowed at 5.5% APR for 10 years → $325.58 a month, $9,069.46 of interest, $39,069.46 paid in total. Paying $100 extra a month pays it off in 86 months (7 years 2 months) and saves $2,754.62 in interest.
Behind the numbers
How a student loan payment is calculated
Every student loan payment is split into interest and principal. The interest part is the remaining balance times the monthly rate (APR divided by 12); the rest of the payment pays down the principal. Because the balance falls each month, the interest share shrinks and the principal share grows, but the payment stays the same until the loan is paid off.
P is the loan amount ($30,000), r is the monthly rate (5.5% ÷ 12 = 0.4583%) and n is the number of monthly payments (120). Total interest is the monthly payment times n, minus the loan amount.
A few comparisons
Payoff comparison: 5, 10, 15 and 20 years
Same loan as the example ($30,000 at 5.5% APR). The table updates when you change the amount or the APR.
| Term | Monthly payment | Total interest | Total paid |
|---|---|---|---|
| 5 years (60 months) | $573.03 | $4,382.09 | $34,382.09 |
| 10 years (120 months) | $325.58 | $9,069.46 | $39,069.46 |
| 15 years (180 months) | $245.13 | $14,122.51 | $44,122.51 |
| 20 years (240 months) | $206.37 | $19,527.89 | $49,527.89 |
The 20-year term costs $367 less a month than the 5-year term, but $15,146 more in interest. The 10-year term sits in the middle: $247 less a month than 5 years, and $4,687 more interest.
Borrow less, pay less.
Pick the shortest term whose payment you can afford. The payment jumps, but the interest saved is often thousands of dollars.
Pay extra whenever you can, even $25 or $50 a month. Every extra dollar goes to principal and shortens the loan.
Check whether your loan is federal or private before you refinance. Refinancing a federal loan into a private one ends IDR, deferment and forgiveness options.
Ask your servicer how extra payments are applied. Some servicers advance your due date instead of cutting the principal unless you tell them otherwise.
Good to know
Your questions, answered.
How does student loan interest work?
Student loan interest accrues daily on your remaining balance: each day's interest is the balance times the APR divided by 365. When you make a monthly payment, part of it covers the interest that built up since your last payment and the rest pays down the principal. Because the balance falls each month, the interest share shrinks and the principal share grows, but the payment stays the same. For example, $30,000 at 5.5% APR costs $325.58 a month over 10 years and $9,069.46 in total interest.
Should I choose a fixed or a variable interest rate?
A fixed rate stays the same for the life of the loan, so your payment never changes. A variable rate starts lower but can rise or fall with the market, so your payment can change. Federal student loans are always fixed. For a private loan, pick fixed if you want a predictable payment, and variable only if you can afford a higher payment later and plan to pay the loan off quickly.
Do extra payments really save money on a student loan?
Yes. Any extra amount you pay goes straight to the principal, which cuts the interest on every payment after it and shortens the loan. On a $30,000 loan at 5.5% APR over 10 years, paying $100 extra a month pays the loan off in 86 months instead of 120 — 34 months sooner — and saves $2,754.62 in interest. Ask your servicer to apply extra payments to principal, and check that there is no prepayment fee.
What is income-driven repayment (IDR)?
Income-driven repayment is a federal program that sets your monthly payment from your income and family size instead of your loan balance — usually 10% to 20% of your discretionary income. Plans include SAVE, PAYE and IBR. Payments can be as low as $0, and any balance left after 20 to 25 years of payments may be forgiven, though the forgiven amount can be taxed. IDR lowers the monthly bill, but because the loan runs longer you usually pay more interest in total.