Student Loan Calculator
✦ Finance & MoneyUse this student loan calculator to estimate your monthly payments, see how in-school interest capitalization increases your starting balance, and discover how extra payments shorten your payoff timeline.
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The formula
Student loan amortization with capitalization
P_{\text{repay}} = P + I_{\text{accrued}}, \quad M = P_{\text{repay}} \times \frac{r(1+r)^n}{(1+r)^n - 1}P = original borrowed principal; I_accrued = simple daily interest accumulated during in-school deferment and grace periods (waived on Subsidized loans); P_repay = capitalized principal at repayment start; r = monthly interest rate (annual rate / 12); n = total repayment months (e.g., 120 for Standard 10-year). Level payments are rounded to the nearest cent; interest computes on unrounded remaining balances. Source: Federal Student Aid, CFPB.
Calculating it by hand
- Enter your total student loan balance or borrowed principal amount.
- Enter the fixed annual interest rate from your promissory note.
- Select your repayment term — the 10-year Standard plan is the federal baseline.
- Choose your loan type (Direct Subsidized, Direct Unsubsidized, or Private).
- Select how many years you were enrolled in school to compute in-school and grace-period interest accrual.
- Optionally enter an extra monthly payment or lump sum in Advanced options.
- Examine the payment breakdown, capitalization impact callout, comparison table, and complete schedule.
Worked examples
Standard 10-Year Unsubsidized Loan with In-School Accrual
Original principal: $30,000; fixed interest rate: 6.53%.In-school & grace duration: 4 years + 6 months = 54 months.Accrued interest: $30,000 x (0.0653 / 12) x 54 = $8,815.50.Starting repayment balance after capitalization: $38,815.50.Monthly payment for 120 months: $441.33 (interest is rounded to the cent each month, so the 120th payment, $442.17, absorbs the residual).Total repayment interest: $14,144.94; Total lifetime cost: $52,960.44.
Monthly payment: $441.33; Total interest paid in repayment: $14,144.94 (plus $8,815.50 accrued in school).
Accelerating a $35,000 Loan with $100/Month Extra Payment
Starting repayment principal: $35,000 at 6.00% over 10 years.Baseline monthly payment: $388.57 (Total interest: $11,628.40).Extra payment: $100.00/month (Total payment: $488.57/month).New payoff timeline: 89 months instead of 120 months (31 months faster).Accelerated total interest paid: $8,440.56.
Debt-free 31 months sooner with $3,187.84 saved in lifetime interest.
Standard 10-Year vs. Extended 25-Year Repayment Comparison
Starting balance: $50,000 at 6.80% fixed rate.10-Year Standard Plan: $575.40/month; Total interest: $19,048.00; Total paid: $69,048.00.25-Year Extended Plan: $347.04/month; Total interest: $54,112.00; Total paid: $104,112.00.Trade-off: Extended plan lowers monthly bill by $228.36/mo but costs $35,064.00 more in interest.
10-Year payment: $575.40/mo ($19,048 interest); 25-Year payment: $347.04/mo ($54,112 interest).
Methodology
How student loan repayment actually works
Student loans differ from ordinary debt because interest that goes unpaid during school and the grace period is usually capitalized — added to the principal when repayment starts — so every later payment carries interest on that interest. The repayment term you choose then sets how much more you pay in total.
Read sources and limitsHow does interest capitalization raise a student loan balance?
The single most critical mechanical difference in student lending is whether the federal government pays your interest while you are enrolled in college. With Direct Subsidized loans, the U.S. Department of Education covers all interest during school enrollment (at least half-time) and during the six-month grace period. Your loan balance upon entering repayment is exactly what you borrowed.
With Direct Unsubsidized loans and private loans, interest begins accruing on day one of disbursement using a simple daily interest formula. If you do not make interest-only payments while in school, all accumulated interest capitalizes when your grace period ends. Capitalization means that unpaid interest is added to your principal balance, becoming part of the new base upon which future interest is charged. On a $30,000 unsubsidized loan at 6.53%, four years of college plus a six-month grace period accrues $8,815.50 in interest, causing you to begin repayment with a $38,815.50 balance.
Is the 10-year standard plan or an extended plan cheaper?
The default repayment plan for federal student loans is the Standard Repayment Plan, which features fixed level monthly payments over 10 years (120 months). This structure minimizes the total interest you pay over the life of the debt and ensures you are debt-free within a decade.
Borrowers with more than $30,000 in federal loans can opt for Extended Repayment Plans spanning 20 or 25 years. While an extended plan significantly lowers your required monthly obligation, it drastically increases your lifetime financing costs. For example, repaying a $50,000 balance at 6.8% over 25 years reduces the monthly payment from $575.40 to $347.04, but increases total lifetime interest from $19,048 to $54,112 — adding $35,064 in finance charges.
How much faster do extra payments pay off a student loan?
Under the Higher Education Act of 1965, federal student loans never carry prepayment penalties. Any payment made above your minimum monthly amount can be directed straight toward reducing your highest-interest principal, provided you instruct your loan servicer correctly, so every extra dollar shortens the schedule.
Making even a modest extra payment of $100 per month on a $35,000 loan at 6% over 10 years saves $3,187.84 in total interest and eliminates 31 months (about 2.6 years) of payments. When submitting extra funds to loan servicers (such as Nelnet, MOHELA, or Aidvantage), specify that excess amounts must be applied to principal rather than advancing the next billing due date.
Why can't this calculator estimate income-driven repayment?
Income-Driven Repayment (IDR) plans — including SAVE, IBR, PAYE, and ICR — calculate monthly payments based on a percentage (typically 5% to 15%) of your discretionary income above federal poverty guidelines rather than loan amortization. Any remaining balance after 20 or 25 years of qualifying payments is forgiven.
Because IDR calculations depend on fluctuating adjusted gross income (AGI), household size, state poverty tables, and ongoing statutory litigation, standard amortization calculators cannot predict IDR payments. Borrowers exploring income-contingent options or Public Service Loan Forgiveness (PSLF) should use the official Loan Simulator on studentaid.gov.
Can you deduct student loan interest?
Under IRS Publication 970 and Section 221 of the Internal Revenue Code, eligible taxpayers can deduct up to $2,500 of student loan interest paid per year as an above-the-line deduction, meaning you do not need to itemize deductions on Form 1040.
The deduction phases out at higher modified adjusted gross income (MAGI) tiers. Tracking your annual interest through Form 1098-E ensures you capture these savings while prioritizing high-rate private debt payoff before attacking low-rate subsidized federal loans.
Student Loan questions
What is the difference between subsidized and unsubsidized student loans?
Direct Subsidized loans are available to undergraduate students with demonstrated financial need; the federal government pays all interest while you are enrolled at least half-time, during the six-month grace period, and during approved deferments. Direct Unsubsidized loans are available to undergraduate and graduate students regardless of financial need, and interest begins accruing immediately upon disbursement.
When does interest capitalize on student loans?
Interest capitalizes on unsubsidized federal loans when your six-month post-graduation grace period ends, when you leave an approved deferment or forbearance, or when you switch out of certain repayment plans. Capitalization adds all accumulated unpaid interest to your principal balance, permanently increasing future interest charges.
How is student loan interest calculated daily?
Federal student loans use a simple daily interest formula: daily interest = (outstanding principal balance x annual interest rate) / 365.25. The interest accrued each day is added to your uncapitalized interest ledger and paid first when your monthly payment is processed.
Can I pay off my student loans early without penalty?
Yes. Federal law strictly prohibits prepayment penalties on all federal and private student loans. You can make extra payments of any size at any time to reduce your principal and shorten your repayment schedule.
Why is my student loan payment higher than expected after graduation?
If you took out unsubsidized loans and did not pay interest during college, four or more years of unpaid interest was capitalized when your grace period expired. This increased your starting principal balance above your original borrowed amount.
How much can I save by paying an extra $100 per month on student loans?
On a typical $35,000 student loan balance at a 6% interest rate, adding $100 per month to the $388.57 standard 10-year payment saves $3,187.84 in interest and makes you debt-free 31 months (about 2.6 years) earlier.
Can I deduct student loan interest on my taxes?
Under IRS Section 221, eligible borrowers can deduct up to $2,500 of student loan interest paid each tax year as an above-the-line deduction on Form 1040, subject to annual modified adjusted gross income (MAGI) phase-out limits.
Why does this calculator not model SAVE or income-driven repayment (IDR) plans?
Income-Driven Repayment plans depend on annual taxable income, family size, state-level poverty guidelines, and evolving statutory regulations that change frequently. Standard amortization models fixed level payments; for income-driven simulations, consult the official Loan Simulator at studentaid.gov.
Source notes
Method, sources & limitations
Every figure on this page comes from the formula above applied to the values you enter. Nothing is estimated from market data, and no result is a forecast. These are the sources behind the method and any fixed figures it uses:
- Federal Student Aid — Understanding Student Loan Interest Rates and Capitalization
- CFPB — Student Loan Repayment Options and Guide
- IRS — Publication 970: Tax Benefits for Education
Educational information only. Results are estimates produced from the assumptions you enter, and are not financial, tax, legal or medical advice. Check anything that matters against a qualified professional and the cited sources.