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//// Financial · Student Loans

What Will Your Student Loan Really Cost You?

You borrowed $30,000. You'll pay back $47,000. See every dollar of interest, every month of payments, and what extra $50/mo does.

Where this fits

💸 Budgeting & Cash FlowCash FlowFoundersStudents

This tool lives inside Cash Flow and is most useful for founders and students.

401(k) Limit 2024$23,000
Roth IRA Limit$7,000
S&P 500 Avg Return~10%/yr

You borrowed $30,000. You'll pay back $40,143.87. Here's why.

$9,318.87 in interest — 31.1% of what you originally borrowed

Quick Presets

Loan Details

Repayment Plan
Loan Type
Monthly Payment
$334.53
10-year plan
Total Paid
$40,144
Started with $30,000
Total Interest
$9,319
Over 120 months
Interest vs Loan
31.1%
The "wow" number

Where Your Money Goes

Principal 77%
Interest 23%
Principal: $30,825Interest: $9,319

Extra Payment Comparison(showing +$50/mo for reference)

ScenarioMonthlyTotal PaidMonthsInterest Saved
Base plan$334.53$40,144120—
+$50/mo$384.53$38,508101$1,636

Adding $50/mo saves you $1,636 in interest and pays off 19 months earlier.

Heads up: Public Service Loan Forgiveness (PSLF) forgives remaining balances after 120 qualifying payments. Income-driven repayment plans forgive remaining balances after 20–25 years. Visit studentaid.gov for details.

1

Interest during school

Subsidized loan — no interest accrues during school

= $0.00

Subsidized loans don't accrue interest while you're enrolled at least half-time. The government covers it. This is worth thousands in savings compared to an unsubsidized loan.

Federal Student Aid — Subsidized vs Unsubsidized Loans (studentaid.gov)

2

Interest during grace period

interest = capitalizedAfterSchool × (rate/12) × gracePeriodMonths

= $30,000.00 × 0.004583 × 6 mo

= $825.00

The 6-month grace period after graduation — interest accrues and gets added to your balance. You haven't made a single payment and you already owe more.

Federal Student Aid — Grace Period definition (studentaid.gov)

3

Capitalized principal (what you actually owe on Day 1 of repayment)

capitalizedPrincipal = principal + interestDuringSchool + interestDuringGrace

= $30,000 + $0.00 + $825.00

= $30,825.00

This is the number that actually matters — your real starting balance. It's $825.00 more than you originally borrowed.

4

Monthly payment (10-year standard amortization)

PMT = P × r(1+r)^n / ((1+r)^n − 1)

P = $30,825.00, r = 0.004583, n = 120

= $334.53/mo

Over 10 years at 5.5% annual interest. Month 1: most of this goes to interest.

Standard amortization PMT formula; IDR calculation — studentaid.gov Loan Simulator

5

Total amount paid over the life of the loan

totalPaid = monthlyPayment × termMonths

= $334.53 × 120 months

= $40,143.87

You borrowed $30,000. You'll pay back $40,143.87. The difference — $9,318.87 — is pure interest.

6

Interest as % of original loan (the "wow" number)

interestPct = totalInterestPaid / originalPrincipal × 100

= $9,318.87 / $30,000 × 100

= 31.1% — you pay 31.1% on top of what you borrowed

For every $1 you borrowed, you'll pay back $1.31. Paying even $50/mo extra dramatically reduces this.

Key insight

You borrowed $30,000. After interest during your grace period, and 10 years of payments, you'll pay back $40,144. The interest rate doesn't sound huge — but compounded over years, it adds up. The single best move: pay a little extra every month.

Use this result in →

Budget Calculator →Net Worth Tracker →Savings Rate →

#ShowYourWork

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