Student Loans
How Student Loan Interest Is Calculated (Daily, Not Monthly)
The daily simple-interest formula servicers use, worked on a real balance, plus how capitalisation compounds the effect.
By Sarah Mitchell · Reviewed by Legamoney Mortgage & Lending Desk
Federal student loans use daily simple interest: balance × rate ÷ 365 × days. Capitalisation is what turns that into compounding.
Key takeaways
- Federal student loans use daily simple interest: balance × rate ÷ 365 × days. Capitalisation is what turns that into compounding.
- Daily interest = principal × annual rate ÷ 365.
- Payments are applied to fees, then accrued interest, then principal.
- Capitalisation adds unpaid interest to principal at defined events.
In this guide
- What matters here
- Point by point
- Daily interest = principal × annual rate ÷ 365
- Payments are applied to fees, then accrued interest, then principal
- Capitalisation adds unpaid interest to principal at defined events
- Paying mid-cycle reduces the balance that accrues for the rest of t…
- A short review checklist
- Questions worth asking
- Worked repayment context
- Practical next steps
What matters here
- Daily interest = principal × annual rate ÷ 365.
- Payments are applied to fees, then accrued interest, then principal.
- Capitalisation adds unpaid interest to principal at defined events.
- Paying mid-cycle reduces the balance that accrues for the rest of the cycle.
Point by point
Daily interest = principal × annual rate ÷ 365
Daily interest = principal × annual rate ÷ 365. This is the part most people skip, and it is where student loan repayment costs money quietly rather than obviously.
Payments are applied to fees, then accrued interest, then principal
Payments are applied to fees, then accrued interest, then principal. Write the answer down before you act on it — an undocumented assumption here is impossible to audit later.
Capitalisation adds unpaid interest to principal at defined events
Capitalisation adds unpaid interest to principal at defined events. Check this against your own paperwork rather than a general guide, because the terms differ between providers.
Paying mid-cycle reduces the balance that accrues for the rest of t…
Paying mid-cycle reduces the balance that accrues for the rest of the cycle. If this changes, everything downstream of it changes too, so review it whenever your circumstances move.
A short review checklist
- Confirm which of the points above actually applies to your situation — several will not.
- Gather the documents that prove each figure you are relying on.
- Model the outcome with your own numbers before accepting anyone else's summary.
- Note the date you checked, because rules and rates on student loan repayment change.
- Keep a copy of any written confirmation you receive.
Questions worth asking
- How does this apply to you: daily interest = principal × annual rate ÷ 365?
- How does this apply to you: payments are applied to fees, then accrued interest, then principal?
- How does this apply to you: capitalisation adds unpaid interest to principal at defined events?
- How does this apply to you: paying mid-cycle reduces the balance that accrues for the rest of the cycle?
Treat the list above as the agenda for a single sitting. Working through 4 specific questions with your own paperwork in front of you settles more about student loan repayment than reading another general explanation, and it produces a written record you can revisit when something changes.
Worked repayment context
Standard 10-year payments at common balances
| Balance | 5.5% rate | 6.5% rate | 7.5% rate |
|---|---|---|---|
| $20,000 | $217.05 | $227.10 | $237.40 |
| $40,000 | $434.11 | $454.19 | $474.81 |
| $60,000 | $651.16 | $681.29 | $712.21 |
| $100,000 | $1,085.26 | $1,135.48 | $1,187.02 |
Practical next steps
- Pull your full loan list from the federal aid system so nothing is missed.
- Note the loan type and servicer for each — eligibility follows the loan type.
- Model the payment under the standard plan and one income-driven plan.
- Document every certification you file, with dates.
Sources
- 01Federal Student Aid (studentaid.gov)
Primary source for federal loan limits, repayment plans and forgiveness rules.
- 02Consumer Financial Protection Bureau — Student loans
Regulator guidance on servicing, repayment and borrower protections.
Frequently asked questions
Where do I find every loan I hold?
Your federal aid account lists all federal loans and servicers. Private loans appear only on your credit report.
Can I change repayment plans later?
Federal borrowers can change plans at any time without a fee. Private lenders rarely allow it.
Does refinancing federal loans lose these options?
Yes. Refinancing with a private lender permanently removes access to federal repayment plans and forgiveness.
Editorial transparency
- Written by
- Sarah Mitchell — Consumer credit writer — personal loans, debt and credit scores
- Reviewed by
- Legamoney Mortgage & Lending Desk — Editorial desk — mortgages, home equity, and consumer credit
- How this was researched
- Worked with the standard published formula for this calculation and checked against the primary sources listed below.
- Corrections
- Spotted an error? Tell us and we will correct and re-date the page. See our editorial policy.
- Advertising disclosure
- Ad placements are clearly labelled and never influence editorial judgement or the ordering of comparisons.
About the author
Sarah Mitchell covers borrowing outside the mortgage: personal loans, credit cards, student debt, debt payoff strategy and how credit scoring actually works. She uses CFPB guidance, the Federal Reserve's G.19 consumer credit release and the federal student aid rules as her reference points, and shows payoff arithmetic in full. She works with the Legamoney Mortgage & Lending Desk.
How this article was checked
- Every factual claim is traced to a named regulator, government agency, or the provider's own published terms before publication.
- Figures that change — rates, limits, thresholds — link to the primary source that publishes them rather than being quoted as a fixed number.
- Worked examples are shown as full arithmetic so a reader can reproduce the result independently.
- Each guide is checked by the owning editorial desk before it is published, and again whenever the underlying rules change.
Covers: Personal loans and loan comparison maths · Credit cards, interest accrual and payoff plans · Debt management and consolidation · Credit scores, reports and disputes
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Disclaimer
Figures on this page are worked examples produced with standard formulas and the assumptions stated. They are not an offer, a quote, or personalised financial advice. Consult a qualified professional before acting on any information here. Read our full disclaimer.