Enter your adjusted gross income, family size, and a payment-rate style, and this calculator estimates a monthly payment using the traditional “discretionary income” formula that federal income-driven repayment plans have used for over a decade. That’s an important caveat, not a footnote: this tool estimates a traditional discretionary-income-style payment, not a guaranteed number from any specific federal plan operating today. Federal IDR policy is genuinely unsettled in 2026 — plans have closed, one was struck down in court, and a new one is still rolling out — so treat the output here as a well-grounded ballpark you can sanity-check your options with, not a bill. For a binding number, the Department of Education’s own loan simulator, reachable through your studentaid.gov account, is the only tool that pulls your actual loan data and current plan rules.
How income-driven payments actually work
Every income-driven federal repayment plan built since the mid-2000s — ICR, IBR, PAYE, REPAYE, and SAVE — has used some version of the same three-step math, and it has nothing to do with your loan balance. It starts with an income exclusion, then applies a percentage to what’s left over.
Step one: subtract an income exclusion tied to family size. The government publishes a poverty guideline every January based on how many people are in your household. IDR plans don’t tax your full income — they exclude a multiple of that guideline first, on the theory that everyone needs some income just to live before student loan payments are even relevant. Most plans use 150% of the poverty guideline as that exclusion; a few older plan variants used a smaller 100% exclusion instead. Whatever is left over after subtracting that exclusion from your adjusted gross income (AGI) is called your “discretionary income.” If your income doesn’t clear the exclusion, your discretionary income is zero — and so is your payment.
Step two: apply a percentage. Plans then take a set percentage of that discretionary income as your annual payment — historically 10%, 15%, or 20% depending on the plan. Divide by 12 and that’s your monthly payment.
Step three: nothing else touches the formula. Your loan balance, your interest rate, your remaining term — none of it enters the calculation. Two people with the same income and family size but wildly different loan balances get the same IDR payment. This is the single biggest way IDR math diverges from the student loan repayment calculator on this site, which does the opposite: it takes your balance, rate, and term and amortizes a fixed payment, the same way a mortgage or car loan works. That fixed-amortization math is accurate for Standard and Tiered Standard federal plans and for private loans. It has no way to model a payment that’s driven by income instead of balance — which is exactly the gap this calculator exists to fill, using the same discretionary-income logic real IDR plans are built on.
Historically, the percentage and exclusion varied by plan. IBR for borrowers with loans from before July 2014 used 15% of discretionary income above a 150% exclusion, with forgiveness after 25 years. IBR for borrowers who took out their first loan on or after July 2014 dropped that to 10%, with forgiveness after 20 years — the same 10%-above-150%-exclusion structure PAYE used starting in 2012 and REPAYE used starting in 2015. The older ICR plan worked differently: it used a smaller 100% exclusion (making more of your income count as “discretionary”) and capped your payment at the lesser of 20% of that discretionary income or what you’d owe on a 12-year standard plan adjusted by an income factor — a more convoluted calculation this estimator doesn’t attempt to reproduce. This calculator’s percentage selector lets you compare a 10%-style estimate against a 15%-style estimate, both using the same 150%-of-poverty-guideline exclusion, so you can see how much that one variable alone changes your number.
Why federal IDR policy is in flux right now
If you’ve tried to research which IDR plan applies to you and come away confused, that’s not a research failure on your part — the landscape has genuinely been in motion. As of mid-2026, here’s roughly where things stand, though this is exactly the kind of detail worth reconfirming before you act on it:
- SAVE is gone. The SAVE plan, which had briefly offered some of the most generous terms of any IDR plan, was vacated by a court order. Borrowers who were on it have been moved off, generally into forbearance or another plan while the details get sorted out.
- PAYE and ICR are closing to new enrollees. Both stopped accepting new borrowers as of July 1, 2026, and are scheduled to sunset entirely by 2028. If you were already enrolled before that date, you may be able to stay on your plan for a while longer, but you can’t newly sign up.
- IBR remains open, with a cutoff. IBR is still available on an ongoing basis, but only for loans first disbursed before July 1, 2026. Loans disbursed on or after that date aren’t eligible for it.
- RAP is the new plan going forward. Repayment Assistance Plan (RAP) launched July 1, 2026 as the primary income-driven option for loans that no longer qualify for IBR. Its published formula is structured differently from the classic discretionary-income plans above — it scales payments roughly 1% to 10% of AGI directly, without the 150%-of-poverty-guideline exclusion step, reduces the payment by a flat amount per dependent, sets a $10 minimum, and forgives any remaining balance after 30 years of qualifying payments.
That last point is exactly why this calculator doesn’t try to reproduce RAP directly. RAP’s income brackets and per-dependent reduction are still being implemented and clarified by loan servicers, and building a calculator around a formula that isn’t fully stable yet risks giving you a number that looks precise but isn’t reliable. The classic discretionary-income formula, by contrast, has over a decade of consistent regulatory history behind it across ICR, IBR, PAYE, and REPAYE — which is why it’s a more honest foundation for an estimate, even though it isn’t the formula every current loan will actually use.
What this estimator does and doesn’t capture
Be clear-eyed about what you’re looking at. This calculator:
- Does apply the classic discretionary-income formula — AGI minus 150% of the poverty guideline for your family size, times a payment-rate percentage you select — to produce a monthly estimate.
- Does not reproduce RAP’s actual formula, or any other current plan’s exact current rules. If your loans are RAP-eligible, your real payment could differ meaningfully from what this tool shows.
- Does not account for forgiveness timelines. Real IDR plans forgive remaining balances after a set number of qualifying payments (typically 20-25 years, 30 for RAP), and interest can accrue faster than a low IDR payment covers it, growing your balance in the meantime. This calculator only estimates a monthly payment figure — it doesn’t project your balance forward or tell you when forgiveness might hit.
- Does not handle married-filing-separately nuances or spousal income rules. Some plans count spousal income and family size differently depending on how you file your taxes and which plan you’re on; this calculator asks for a single AGI and family size and applies the formula uniformly, which won’t match every household’s real situation.
- Does not know your actual loan balance, rate, or servicer records. It has no connection to your real loans — it’s a standalone formula calculator, not a portal into your account.
For anything you’re about to act on — switching plans, recertifying income, deciding whether to consolidate — use the official loan simulator tied to your studentaid.gov account. It pulls your real loan data and applies the actual current rules for your specific loans, which is something no standalone calculator, including this one, can do. If you’re weighing whether to consolidate older loans to change which plans you’re eligible for, the loan consolidation calculator on this site can help you see the interest-rate and balance effects of that decision separately from the IDR question. And if a fixed-rate refinance might beat a high IDR payment over time — usually only worth considering if you’re confident you won’t need IDR or federal forgiveness options — the student loan refinancing calculator runs that comparison.
Family size and why it matters
Family size does more work in this formula than most people expect, because it changes the size of the exclusion before any payment math even starts. A single borrower and a borrower supporting a family of four with the exact same AGI can end up with meaningfully different discretionary income, because the four-person household gets a much larger chunk of income excluded first.
Concretely: at 150% of the poverty guideline, each additional household member raises your exclusion by several thousand dollars a year. For someone whose income sits close to that exclusion line, adding a dependent can be the difference between owing a real monthly payment and owing nothing at all. For someone with income well above the exclusion regardless of family size, the effect is smaller in relative terms but still shows up as a real dollar reduction in the payment.
“Family size” for these plans generally means the number of people you claim on your tax return, plus yourself and, in most cases, a spouse if you file jointly — not just dependents in the everyday sense. If your household composition changes (a child is born, a dependent ages out, your marital status changes), your real IDR payment would be recalculated at your next annual recertification. This calculator lets you test that by changing the family size field and comparing the two payment estimates side by side.
FAQ
Is this the same as the official IDR payment I’d actually be charged? No. It’s a well-established formula — the same discretionary-income math IBR, PAYE, and REPAYE have used for years — applied to the income and family size you enter. Your real payment depends on which specific plan you’re enrolled in, your exact loan history, and rules (like RAP’s newer formula) that this calculator deliberately doesn’t attempt to reproduce. Use it as a planning estimate, then confirm with the official loan simulator before making a decision.
Why does the calculator ask for family size, not just my income? Because the formula excludes a portion of your income before applying any payment percentage, and that excluded amount scales directly with how many people are in your household. Larger families get a bigger exclusion, which lowers or eliminates the payment even at the same income level as a smaller household.
What poverty guideline figures does this calculator use? The most recently published federal poverty guidelines for the 48 contiguous states and DC, updated annually every January. Guidelines differ for Alaska and Hawaii under the real federal program; this calculator uses the contiguous-states figures for everyone, so borrowers in Alaska or Hawaii should treat the output as a rougher estimate.
Which payment-rate option should I pick? If you’re not sure which historical plan style is closest to your situation, try both the 10% and 15% options and treat the range between them as your estimate rather than picking one number as definitive. The 10% rate matches how PAYE and REPAYE (and post-2014 IBR) calculated payments; the 15% rate matches pre-2014 IBR. Neither is guaranteed to match RAP, which uses a different formula entirely.
Why doesn’t this calculator just model RAP directly, since that’s the newest plan? RAP’s income brackets, per-dependent reduction, and implementation details were still being finalized and clarified by servicers as of when this calculator was built. Rather than hard-code a formula that might be wrong or incomplete, this tool sticks to the classic discretionary-income math that’s been stable and well-documented for over a decade, and says so plainly. Check studentaid.gov or your servicer directly for RAP-specific numbers.
Does a lower IDR payment mean I pay less overall? Not necessarily. A lower monthly payment can mean your balance grows faster than you’re paying it down, since interest keeps accruing. IDR plans are generally about affordability and eventual forgiveness after a long payment window, not about minimizing total interest paid — that’s a very different goal from the fixed-payment payoff math in the student loan repayment calculator, which is built to show you exactly how much interest a fixed schedule costs over time.