Almost every private student loan offers the same four choices: pay nothing in school, pay $25 a month, pay just the interest, or start full payments immediately. The gap between the cheapest and most expensive option on a $30,000 loan is $9,919, and it's decided at signing, not at graduation. Here's what each mode does.
Same loan throughout: $30,000 at 9.49% fixed, four years in school, ten years of repayment after. That rate is realistic for a 2026-27 private loan without a top-tier cosigner.
| Mode | In school | Balance at graduation | Payment after | Total interest |
|---|---|---|---|---|
| Full deferral | $0 | $41,388 | $535.32 | $34,239 |
| Flat $25/mo | $25 | $40,188 | $519.80 | $33,576 |
| Interest-only | $237.25 | $30,000 | $388.03 | $27,951 |
| Immediate | $323.33 | $24,998 | $323.33 | $24,320 |
Interest doesn't sleep during school. Each month of deferral adds roughly $237 of interest (30,000 × 0.0949 ÷ 12) as simple interest on the principal you borrowed. Private lenders don't compound that pile month to month; they let it sit and then capitalize it once, at the end of the grace period. Four years of it adds $11,388, so $30,000 becomes $41,388 before your first real payment, and then the whole $41,388 amortizes for ten years at 9.49%. Capitalization is the event that costs you, not in-school compounding.
Check the interest-only row to see the counterfactual: same loan, same rate, same school. The only difference is that the $237 a month of new interest gets paid off before it can capitalize. Balance never grows, payment after school is $147.29 lower, and total interest drops by $6,287. Nothing about the loan's terms changed. Timing did.
The honest hierarchy: immediate beats interest-only beats flat $25 beats deferral, in every case, at any rate. The constraint is cash flow, not knowledge. So the real question is what you can earn while enrolled:
Run your actual loan amount and rate in the private student loan calculator; the interest-only threshold scales linearly, about $79 of monthly interest per $10,000 borrowed at 9.49%.
Amount, rate, years in school, and each mode's true cost, with the capitalization reveal.
Private Student Loan Calculator →Private loans have one big advantage over federal: refinancing them risks nothing. Two or three years of on-time payments and a real income can turn a 9.49% student rate into a 6% refinance. On the deferral example, refinancing the $41,388 balance from 9.49% to 6.5% after graduation cuts the payment from $535.32 to $469.95 and saves about $7,800 over the decade. The refinance calculator prices your exact numbers.
One caution before borrowing private at all: exhaust federal Direct first. Federal loans bring the RAP income-based plan and its 30-year (360-payment) forgiveness track, which private loans never will. If you're weighing the two, our RAP calculator shows what the federal side would charge at your expected income, and the consolidation calculator handles the federal side if you already have a mix.
Usually yes, that's the default at most lenders, and sometimes for six months after graduation too. But deferment doesn't pause interest, it pauses payments. Interest accrues from disbursement and capitalizes (joins the principal) when repayment starts. On $30,000 at 9.49% over four years, that's $11,388 added to the balance you'll pay interest on for the next decade.
On $30,000 at 9.49%, interest-only costs $237.25 a month during school and cuts total interest from $34,239 to $27,951, a savings of $6,287. It also drops the post-graduation payment from $535.32 to $388.03. If a part-time job can cover roughly $240 a month, it's the highest-return money a student can spend.
Many lenders (Sallie Mae popularized it) offer a flat $25 monthly payment while you're in school. It's a psychological product more than a financial one: on the example loan it reduces capitalized interest from $11,388 to $10,188, saving about $663 in total interest. Every dollar still beats deferral, but it's an order of magnitude weaker than interest-only.
No. Income-driven plans, including the new federal RAP plan, apply only to federal loans. Private lenders offer their own hardship programs, usually short forbearances or interest-only periods, and some offer modified terms after graduation. Nothing scales payments to income automatically, which is one reason to exhaust federal Direct loans before borrowing private.
Educational content, not financial advice. Lender terms vary; read your promissory note for the exact options on your loan.