How it works
Capitalized interest is unpaid accrued interest that gets folded into principal — typically when a student loan exits its school and grace periods — after which the loan charges interest on the combined amount. Until that moment, accrued interest sits beside the balance doing nothing; the instant it capitalizes, it begins earning interest exactly like borrowed money, which is why capitalization is the single most expensive quiet event in student lending. The calculator quantifies the damage two ways. First, the accrual: a $28,500 unsubsidized-style balance at 6.4% left untouched for three school-plus-grace years accumulates roughly $5,500 of unpaid interest, lifting the day-one repayment balance near $34,500. Second, the consequence: amortizing the inflated balance costs measurably more per month and dramatically more per decade than amortizing the original balance while paying the school-time interest as it went — the difference is the capitalization penalty shown as the hero number. The amortization table beneath shows the capitalized loan month by month so you can watch the folded-in interest retire slowly. The strategic lesson generalizes: any moment interest can capitalize — forbearance exits, plan switches, grace ends — paying even interest-only amounts beforehand is usually the cheapest money you will ever save.
Formula
Capitalized balance = P × (1 + r/12)^(12 × years) | Penalty = total repaid on capitalized balance − (P + simple school interest + repaid principal interest)
Tips
- Pay interest monthly during school if unsubsidized — it neutralizes capitalization entirely.
- Expect capitalization events at graduation, grace-end, and after forbearance exits.
- Even partial interest payments shrink the base that later compounds.
- Ask servicers whether a lump-sum catch-up before the event beats post-event repayment — it always does arithmetically.
- Watch plan-switch terms on income-driven plans; some transitions capitalize accrued interest.
Frequently asked questions
- What does capitalization mean on a student loan?
- Unpaid interest is added to principal, becoming part of the amount that itself accrues interest going forward. A $28,500 balance carrying three years of unpaid 6.4% interest grows to about $34,500 at repayment — and every future charge computes on that larger figure.
- When does interest capitalize on student loans?
- Commonly at the end of school and grace periods for unsubsidized loans, after certain forbearances, and on some plan changes or delinquency recoveries. Each event folds whatever has accumulated into principal at once, which is why timing a payoff just before the event saves double.
- How much extra does capitalization actually cost?
- On these defaults, letting $28,500 accrue unpaid for three years adds roughly $5,800 of interest, then compounds it — the all-in penalty versus paying along the way approaches several thousand dollars more over a ten-year term, plus a meaningfully higher monthly payment from day one.
- Is it better to pay interest during school?
- Almost always, if cash allows. Paying the accruing interest keeps the balance flat, avoids every compounding effect, and on these defaults saves about $2,600 across repayment — roughly $5,500 never gets the chance to capitalize. Interest-only school payments are among the highest-certainty returns available to students, so start the habit in year one for maximum effect.
- Does capitalization happen on subsidized loans?
- Subsidized federal loans generally do not accrue interest during in-school deferment, so there is nothing to capitalize from that period — though other events, like certain forbearances, can still trigger capitalization. Unsubsidized and private loans carry the full exposure described here.