Every income-driven repayment plan runs on the same two-step formula: calculate your discretionary income, then take a set percentage of it as your annual payment. The plans differ only in which percentage and which multiple of the federal poverty guideline they use to define "discretionary." Once you understand those two inputs, you can approximate your own payment without waiting on a servicer's portal to load.
How it works
The formula has three moving parts, applied in order.
- Start with your adjusted gross income (AGI) from your most recent tax return, or your spouse's combined AGI if you file jointly and your plan counts it.
- Subtract a multiple of the federal poverty guideline for your family size. Older plans like IBR and ICR generally use 150% of the guideline; newer plans use a larger multiple, commonly 225%, which shelters more income from the calculation.
- Apply the plan's percentage — typically 10% to 20% annually — to whatever income remains after that subtraction. Divide by 12 for your monthly bill.
The subtraction step is why family size matters so much: the poverty guideline rises with each additional household member, which increases the amount protected before any percentage is applied.
A worked example
Assume a single borrower, family size of one, with an AGI of $52,000. Using a hypothetical poverty guideline of $15,000 for a household of one — confirm the actual current figure for your family size on the Department of Health and Human Services site, since it updates annually.
| Step |
225%-multiple plan |
150%-multiple plan |
| Poverty guideline (hypothetical) |
$15,000 |
$15,000 |
| Multiple applied |
225% |
150% |
| Protected income |
$33,750 |
$22,500 |
| AGI |
$52,000 |
$52,000 |
| Discretionary income |
$18,250 |
$29,500 |
| Payment percentage |
10% |
15% |
| Annual payment |
$1,825 |
$4,425 |
| Monthly payment |
~$152 |
~$369 |
The same income and the same balance produce more than a $200 monthly swing depending only on which plan's multiple and percentage apply. This is why confirming your actual plan name, not just that you are "on an income-driven plan," matters before you budget around a number.
How family size and recertification change the number
- Add a dependent, and the protected-income floor rises, which lowers discretionary income and therefore your payment — report household changes to your servicer as they happen, not just at recertification.
- Married filing separately can shrink the AGI counted on some plans, though you lose certain other tax benefits, so run both filing scenarios before choosing.
- Recertify every year, on time. Your payment is only ever a snapshot of last year's income; missing the recertification deadline typically reverts your payment to the standard 10-year amount until you resubmit.
- A payment of $0 is a valid output. If discretionary income calculates to zero or the AGI falls below the protected floor entirely, the formula can produce a $0 monthly payment, and that month still generally counts toward forgiveness on most plans.
- Interest can still accrue even at a low payment, which is why some balances grow before they eventually shrink under these plans — a separate issue from whether the calculation itself is working correctly.
Common mistakes
Using last year's poverty guideline. The figure is updated annually and published by family size — an outdated number throws off any estimate you run by hand.
Forgetting a spouse's income can be included. Depending on the plan and how you file taxes, joint income may factor into the calculation even if only one spouse holds the loans.
Not reporting income drops immediately. You do not have to wait for annual recertification to request a recalculation if your income drops significantly — doing so can lower your payment right away.
Confusing the percentage with the multiple. The poverty-guideline multiple (150% vs 225%) and the payment percentage (10% vs 15% vs 20%) are two separate levers — changing one without the other gives a wrong estimate.
FAQ
Where do I find my exact discretionary income number?
Your servicer's portal and the Loan Simulator on StudentAid.gov calculate it directly from your submitted income and family size — treat manual math as an estimate, not a final figure.
Does discretionary income use gross income or take-home pay?
Adjusted gross income from your tax return, which is neither your gross salary nor your take-home pay — it already reflects certain above-the-line deductions.
What if my income changes mid-year?
You can request an income recalculation before your annual recertification date, which is worth doing promptly if your income drops.
Can my payment go up even if my income stays flat?
Yes, if the poverty guideline for your family size changes, if you recertify late and revert to a standard payment, or if your plan's rules are updated.
Where to go next
For the current status of the plans themselves after recent policy changes, see student loan forgiveness updates for 2026. If you are weighing whether to leave income-driven repayment altogether, read student loan refinance vs forgiveness in 2026, and build your expected payment into how to make a budget spreadsheet in 2026.