Student loan payment estimator — RAP, IBR, PAYE, ICR

What the calculator computes and why the plans diverge

Every federal repayment plan is built on the same structural idea — tie the monthly payment to what the borrower earns rather than what the borrower owes — but the plans split into two families that implement it very differently, and the calculator runs both at once. The older income-driven plans charge a percentage of discretionary income, so their results diverge according to two parameters: the percentage claimed, and how large a multiple of the federal poverty guideline is subtracted from adjusted gross income before that percentage is applied. RAP, the plan that took over on July 1, 2026, throws the concept out entirely.

RAP charges a flat percentage of your whole AGI, with no poverty-line deduction at all: 1% on AGI between $10,001 and $20,000, climbing a point per $10,000 band up to 10% above $100,000. Divide by twelve, subtract $50 for each dependent, and the result cannot fall below $10 a month. Two consequences follow, and the estimator surfaces both. The first is that for many lower earners RAP costs more per month than SAVE did — the single borrower on $40,000 who paid about $17 under SAVE owes roughly $100 under RAP. The second is the cliff: because the percentage is flat rather than marginal, crossing a band edge re-prices every dollar you earn. At $40,000 the bill is 3% of income; at $40,001 it is 4% of income, about $400 more a year for one extra dollar. In exchange RAP waives unpaid interest each month and adds up to $50 toward principal, so the balance cannot grow — the negative-amortization trap of the older plans simply does not arise. Forgiveness, though, waits 360 payments: thirty years. Our full guide to the RAP formula works through the bands and the dependent offset in detail.

SAVE, the newest plan (formerly called REPAYE and restructured under the Biden administration's 2023 rulemaking), is the most generous on both fronts for undergraduate borrowers: it uses only 5% of discretionary income and defines the poverty-level exclusion at 225% of the federal poverty guideline. For a single borrower earning $50,000, SAVE shelters the first $35,910 of income from the payment calculation, then takes 5% of the remaining $14,090, producing a monthly payment of roughly $59. The same borrower under IBR (post-2014 version) shelters only $23,940 (150% of the poverty guideline) and pays 10% of the remainder, producing roughly $217 per month — more than three times higher. Under old-IBR, the rate climbs to 15%, and the payment reaches roughly $326. Under ICR, the shelter drops to 100% of the poverty level and the rate rises to 20%, yielding roughly $567 per month. These are not rounding differences; the plan choice can determine whether a borrower's monthly student loan obligation is manageable alongside rent and groceries or whether it crowds out the rest of the budget.

The poverty guideline and family size

The federal poverty level published annually by the Department of Health and Human Services is the baseline that all IDR formulas reference. For the 2026 guideline year (which applies to the contiguous 48 states and the District of Columbia), the poverty level for a household of one is $15,960. Each additional family member adds $5,680, so a family of four has a poverty guideline of $33,000. Alaska and Hawaii have higher guideline figures and are not modeled in this calculator.

Family size in the IDR context includes the borrower, a spouse (unless filing separately under plans that honor Married Filing Separately), and any dependents claimed on the borrower's federal income tax return. Adding a dependent — a child, for instance — increases the poverty-level exclusion and reduces the monthly payment across every discretionary-income plan. For a borrower earning $50,000, moving from a family size of one to a family size of three shifts the SAVE payment from $59 per month down to $0, because the 225% exclusion for a family of three ($61,470) exceeds the borrower's entire $50,000 income. This is one of the most financially consequential — and least discussed — interactions in the student loan system: family composition directly reduces the monthly obligation through the poverty guideline arithmetic.

RAP reaches the same destination by a blunter route. Dependents do not enlarge any exclusion, because RAP has none; instead each one subtracts a flat $50 from the monthly bill. The same $50,000 borrower pays 4% of AGI — $2,000 a year, about $167 a month — and two dependents take it to $67. A third would take the arithmetic to $17, and a fourth would push it negative, at which point the $10 floor catches it. Notice what that means at the bottom of the income scale: the older plans can and do produce a $0 bill, while RAP never can. Enter your own family size above and the estimator applies whichever rule the selected plan actually uses.

Where the loan balance actually matters

The formulas themselves are a function of how much you earn, not how much you owe. A borrower with $25,000 in federal loans and a borrower with $200,000 will compute the same payment if their AGI and family size are identical. One rule breaks that symmetry, and it is the reason this calculator asks for a balance and an interest rate rather than treating them as decoration: under IBR and PAYE the bill can never exceed what you would pay on the 10-year Standard plan. The estimator amortizes that Standard figure from your balance and rate, applies it as a ceiling, and flags the row as capped when it bites. The effect is counterintuitive — it rewards a modest balance. A borrower earning $95,000 with a family of one computes about $592 a month under new IBR, but if the balance is $30,000 at 6.39% the Standard payment is roughly $339, and $339 is what they owe. Above that income the plan stops lowering the bill at all and merely keeps the borrower on the clock toward forgiveness. RAP and ICR have no such ceiling: RAP because it was written without one, ICR because its statute substitutes a 12-year adjusted figure this calculator does not model.

This design is deliberate — income-driven repayment is an affordability mechanism, not an amortization schedule — but it produces a structural tension. When monthly payments are low relative to accruing interest, the loan balance grows each year (negative amortization). After 20 or 25 years of payments, the remaining balance is forgiven. The American Rescue Plan Act exclusion that made IDR forgiveness tax-free expired on December 31, 2025, so beginning in 2026 that forgiven balance is once again taxable ordinary income in the year of discharge — the so-called "tax bomb" (PSLF forgiveness stays tax-free). See our student loan tax bomb analysis.

For borrowers pursuing Public Service Loan Forgiveness (PSLF), the calculus is different: PSLF discharges the remaining balance after 120 qualifying payments (10 years of full-time public service employment), and PSLF forgiveness is tax-free by statute. The interaction between IDR plan choice and PSLF is covered in detail in the IDR plans deep dive, but the short version is that PSLF borrowers should generally choose the plan that minimizes monthly payments, because every dollar paid before forgiveness is a dollar that would have been discharged tax-free. For non-PSLF borrowers, the analysis is more complex: lower payments mean more negative amortization, a larger forgiven balance, and a potentially larger tax bill at the end of the repayment term.

What replaced SAVE — RAP and the IBR fallback

SAVE was challenged in federal court almost immediately after its final rule took effect, and was ultimately struck down. Its hallmark interest-free forbearance ended and interest resumed on SAVE loans on August 1, 2025. Under the 2025 reconciliation law the plan was replaced by the Repayment Assistance Plan (RAP), live since July 1, 2026, with IBR the surviving traditional plan. Borrowers on the phased-out plans have until July 1, 2028 to switch to RAP or IBR. Verify your options at studentaid.gov before recertifying.

If SAVE is unavailable, IBR is the default statutory fallback for most borrowers with Direct Loans. PAYE is available only to a narrower population (no outstanding loan balance before October 2007, with a disbursement on or after October 2011). ICR is available to all Direct Loan borrowers and is the only IDR plan that accepts parent PLUS loans after consolidation into a Direct Consolidation Loan — but its terms are the least favorable, with a 20% rate against only 100% of the poverty guideline. The comparison table in the widget above lets you see the payment under every plan simultaneously, so the fallback decision has numbers behind it rather than guesswork.

When refinancing into a private loan makes sense — and when it does not

A borrower on IDR who sees a private lender offering a 5.0% fixed rate against their 6.8% federal rate faces a real temptation: the rate spread is visible, the savings are computable, and the application takes ten minutes. What the rate-spread calculation does not price is the permanent loss of IDR eligibility, PSLF eligibility, deferment during hardship, and discharge protections (death, disability, school closure) that attach to federal loans by statute and that a private refinance extinguishes the moment the federal balance is paid off. The full framework for evaluating whether a refinance is net-positive or net-negative for a specific borrower is documented in the federal vs private student loan refinance comparison. The short heuristic: if you are pursuing PSLF, are on a low-payment IDR plan, or have any realistic expectation of needing hardship forbearance in the future, refinancing into a private loan is almost certainly a net loss disguised as a rate improvement.

What this calculator deliberately leaves out

Several things, all material — though the 10-year Standard cap is no longer one of them: it is modelled above, from the balance and rate you enter, and the table marks the row when it binds. What the calculator still leaves out starts with ICR's own ceiling, which the statute builds from a 12-year amortization adjusted by an income factor rather than the flat 10-year figure, so a high-income ICR estimate here reads higher than the real bill. It does not model the RAP principal match, the $50 a month the Department adds when your own payment does not reduce principal by that much — a balance effect, not a payment effect, but the reason a RAP balance falls even at the $10 floor. It does not model the interest subsidy under SAVE, which covers all unpaid interest on subsidized loans and half on unsubsidized loans during periods of $0 or reduced payments. It does not model tax filing status interactions — Married Filing Separately on PAYE and IBR uses only the borrower's individual income, while Married Filing Jointly uses combined household AGI, and the optimal filing choice requires modeling the tax cost of MFS against the IDR payment savings. And it does not project total cost over the repayment term, which requires assumptions about income growth, family size changes, and forgiveness timing that would make the output speculative rather than mechanical. The widget gives you the monthly payment under today's inputs; the long-term projection requires a different kind of analysis.