LOANS & DEBT
Student Loan Calculator — Standard & Income-Based Repayment
By Worldtickers ·
Calculate your standard fixed student loan payment and compare it against a simplified, illustrative income-based repayment (IBR) estimate. See both monthly payments side by side, the formulas behind each, worked examples, and the real limitations of income-driven repayment math.
This student loan calculator — standard & income tool focuses on calculating your standard fixed student loan payment and compare it against a simplified, illustrative income-based repayment (IBR) estimate. See both monthly payments side by side, the formulas behind each, worked examples, and the real limitations of income-driven repayment math. Use it to compare borrowing costs, monthly payments, interest charges, payoff timelines, and refinance or repayment choices by changing the rate, term, balance, and payment assumptions.
Student Loan Calculator
Student Loan Calculator
Switch tabs to edit either the standard loan inputs or the income-based inputs — every calculation shows both monthly payments together so you can compare them directly.
The income-based repayment figure is a simplified, illustrative estimate only — real federal plans (IBR, PAYE, SAVE) use official, annually updated poverty guidelines and additional rules. It is not financial or loan-servicing advice.
Standard vs. Income-Based Repayment
Most student loan borrowers start on a standard repayment plan: a fixed monthly payment, calculated the same way as a mortgage or car loan payment, that pays off the balance in full over a set term. For federal loans, that default term is 10 years. It is predictable and typically the cheapest path in total interest, but the fixed payment does not adjust if your income drops, changes jobs, or takes a career break.
Federal student loans also offer income-driven repayment plans — historically including Income-Based Repayment (IBR), Pay As You Earn (PAYE), and the newer SAVE plan — that tie your monthly payment to how much you earn rather than how much you owe. Instead of a fixed dollar amount, your payment becomes a percentage of your "discretionary income," which is your income above a threshold tied to the federal poverty guideline for your household size.
This calculator lets you compute both side by side. The standard mode uses the exact loan amortization formula lenders use. The income-based mode uses a simplified version of the real discretionary-income math — illustrative, not official — so you can see the shape of the trade-off: a income-driven payment is often lower today, but it can extend your timeline and total interest cost, and in some cases may not even cover the interest accruing each month. Pair this with our Debt-to-Income Ratio Calculator to see how either payment fits into your overall monthly budget.
How to Use This Calculator
The calculator has two tabs. Switching between them does not erase your other inputs — both sets of numbers are kept together so the results panel can always show a side-by-side comparison of your standard payment and your illustrative income-based payment.
Standard Repayment
Enter your current loan balance, your interest rate, and your repayment term in years (10 is the standard federal default, but enter whatever term applies to your loan). Click calculate to get the fixed monthly payment using the standard amortization formula.
Income-Based Repayment (Illustrative)
Enter your annual gross income, your family size (this changes the poverty-line threshold used in the math), and the IBR payment percentage — typically somewhere between 10% and 15% depending on the real-world plan you're comparing against. The calculator computes an illustrative discretionary income and the resulting monthly payment.
Either way, click "Calculate Both Payments" and the results panel will show your Standard Monthly Payment and your Illustrative IBR Monthly Payment together, along with the poverty line and discretionary income figures used behind the scenes.
The Formulas Explained
Standard repayment uses the same amortization formula as any fixed-rate installment loan: M = P × r × (1+r)^n / ((1+r)^n − 1), where P is the loan balance, r is the monthly interest rate (annual rate ÷ 12 ÷ 100), and n is the number of monthly payments (years × 12).
Illustrative income-based repayment works in three steps. First, an illustrative poverty line is estimated from family size: roughly $15,060 per year for a household of one, plus about $5,380 for each additional household member (these are simplified 48-contiguous-states figures for education purposes — real guidelines change annually and differ by location). Second, discretionary income is calculated as max(0, Annual Income − 1.5 × Poverty Line). Third, the monthly IBR payment is Discretionary Income × IBR% / 12.
Notice the 1.5 multiplier and the discretionary-income structure mirror how several real federal income-driven plans are built — they also subtract a multiple of the poverty guideline before applying a percentage. The constants here are simplified and rounded specifically so you can see the mechanics clearly; they are not the exact numbers your loan servicer would use.
Worked Examples
Example 1: Standard 10-Year Repayment
A $30,000 balance at a 6% interest rate over the standard 10-year term: r = 6% / 12 = 0.5% monthly, n = 120 payments. Plugging into the amortization formula gives a monthly payment of approximately $333.06.
Example 2: Income-Based Repayment for a Single Borrower
The same borrower earns $45,000 a year and has a family size of 1. The illustrative poverty line for one person is $15,060. Multiplying by 1.5 gives $22,590. Discretionary income is $45,000 − $22,590 = $22,410. At a 10% IBR rate, the annual payment is $2,241, or approximately $186.75 per month — noticeably lower than the $333.06 standard payment, though likely stretched over a much longer timeline in a real income-driven plan.
Example 3: A Larger Family Can Reduce the Payment to Zero
Same $45,000 income, but a family size of 4. The illustrative poverty line becomes $15,060 + 3 × $5,380 = $31,200. Multiplying by 1.5 gives $46,800 — which is higher than the $45,000 income. Discretionary income floors at $0, so the illustrative IBR payment is $0.00 per month. This mirrors a real and common outcome in federal income-driven plans: low-to-moderate income relative to household size can produce a required payment of zero, even though interest may still accrue on the balance.
Example 4: Higher Income With a 15% Plan
A borrower earning $70,000 with a family size of 1, using a 15% IBR rate (matching plans with a higher percentage than the default 10%): discretionary income is $70,000 − $22,590 = $47,410. At 15%, the annual payment is $7,111.50, or approximately $592.63 per month — illustrating how both a higher income and a higher plan percentage push the income-based payment up.
Tips and Limitations
This IBR Mode Is Illustrative, Not Official Guidance
Real federal income-driven repayment plans (IBR, PAYE, SAVE) use exact, legally defined poverty guidelines, your actual adjusted gross income from tax filings, plan-specific rules by loan type, and features like interest subsidies this calculator does not model. Always confirm your real payment using the official Loan Simulator at studentaid.gov or your loan servicer before making decisions.
Poverty Guidelines Change Every Year
The federal poverty guidelines used in real repayment calculations are updated annually and differ for Alaska and Hawaii versus the 48 contiguous states. The figures used here are simplified, rounded stand-ins for education, not the current official numbers for any given year.
Interest Can Still Accrue Under Income-Based Repayment
A lower monthly payment does not necessarily mean a smaller loan balance is guaranteed. If a payment (including a $0 payment) is smaller than the interest accruing that month, the shortfall can add to the balance over time on some plans, depending on program-specific interest subsidy rules.
Look at Total Cost, Not Just the Monthly Payment
A lower monthly payment stretched over a longer timeline can mean paying substantially more interest over the life of the loan. Weigh short-term cash-flow relief against the total cost and any forgiveness timeline before deciding between plans.
Refinancing Federal Loans Forfeits These Options
If you refinance a federal student loan into a private loan to get a lower rate, you permanently lose access to federal income-driven repayment, deferment, and forgiveness programs. See our Student Loan Refinance Calculator for the math on refinancing, and the trade-offs to weigh first.
Frequently Asked Questions
What is a student loan calculator and how does it work?
A student loan calculator estimates your monthly payment from three numbers: your loan balance, your interest rate, and your repayment term. Under a standard repayment plan it applies the same fixed-payment amortization math used for mortgages and auto loans — the same payment every month until the balance reaches zero. This calculator goes one step further by also estimating a simplified income-based payment, so you can see roughly how a fixed payment compares to one tied to what you earn.
What is the standard federal student loan repayment term?
For federal student loans, the Standard Repayment Plan defaults to a 10-year term — 120 equal monthly payments — which is why this calculator uses 10 years as its default. Borrowers with larger balances can sometimes access Extended Repayment plans running up to 25 years, which lower the monthly payment but increase total interest paid. Private student loans set their own standard terms, commonly 5 to 20 years, so always check your actual loan documents.
How does income-based repayment work in real life?
Real federal income-driven plans (IBR, PAYE, and SAVE) calculate a "discretionary income" by subtracting a multiple of the federal poverty guideline for your household size from your income, then charge a set percentage of that discretionary income — commonly somewhere in the 5% to 15% range depending on the specific plan and loan type. This calculator's IBR mode mirrors that same structure using 150% of an illustrative poverty line and a percentage you choose, to demonstrate the mechanics.
Is the income-based repayment estimate on this calculator official?
No. This is a simplified, educational illustration, not an official federal calculation. Real programs use exact, annually updated Department of Health and Human Services poverty guidelines (which differ for Alaska and Hawaii), your actual adjusted gross income from a recent tax return, specific rules by loan type and plan, and features like interest subsidies or payment caps that this calculator does not model. For your actual required payment, use the official Loan Simulator at studentaid.gov or contact your loan servicer.
What counts as discretionary income for repayment plans?
In both this calculator and most real federal plans, discretionary income is your annual income minus a multiple (150% here, matching several actual programs) of the poverty guideline for your family size. If your income is at or below that multiplied threshold, discretionary income — and therefore your required payment — is treated as zero. This is why family size directly affects your income-driven payment: a larger household gets a larger income exemption before any payment is required.
Should I choose standard repayment or income-based repayment?
It depends on your goals. Standard repayment pays off the loan fastest and usually minimizes total interest, but the fixed payment can strain a tight budget. Income-based repayment lowers your monthly payment when income is low relative to your balance and may lead to loan forgiveness after a qualifying period on federal loans, but it commonly stretches out the repayment timeline and can result in more total interest paid, or even negative amortization if the payment doesn't cover accruing interest. Compare both modes above, and weigh cash-flow needs against total cost.
Does family size really change my required student loan payment?
Yes, under real income-driven federal plans and in this calculator's illustrative model. The poverty guideline used to compute discretionary income rises with each additional household member, so a borrower supporting a larger family has a higher income threshold before any payment is required, and a lower payment above that threshold, all else being equal. Try changing the Family Size field above with the same income to see the payment change directly.
How is a student loan payment different from a personal loan payment?
The underlying monthly-payment math is identical — both use standard loan amortization based on balance, rate, and term. What makes student loans different is the menu of government-backed alternatives layered on top: income-driven repayment, deferment and forbearance, subsidized interest on some loans, and forgiveness programs for qualifying borrowers. Personal loans, by contrast, are almost always fixed-payment products with no income-based alternative. See our Personal Loan Calculator and Debt-to-Income Ratio Calculator to see how a student loan payment fits into your broader debt picture.