Standard Plan Vs Income Driven Student Loan Comparison Tool for Recent Graduates

October 11, 2026 · By The EduRepay Editorial Desk

Will an income-driven repayment plan actually save a recent graduate money compared to the standard 10-year plan?

Let's say you're building a repayment comparison tool for recent graduates. Your user has $45,000 in federal Direct Unsubsidized Loans at 6.8% interest, a starting salary of $55,000, and expects roughly 4% annual salary growth. They're choosing between the standard 10-year plan and the SAVE (formerly REPAYE) income-driven plan. The math isn't intuitive—lower monthly payments sound great when you're entry-level, but total interest over 20 or 25 years can dwarf what you'd pay under standard repayment. I've built these models before, and the break-even point almost always surprises people. Let me walk you through the actual numbers and show you how a comparison tool should handle them.

What is the difference between standard and income-driven repayment?

The standard plan is dead simple: you take the loan balance, apply the interest rate, and divide into 120 equal monthly payments over 10 years. No income checks, no recalculations. You pay the same amount every month until the loan is gone.

Income-driven repayment (IDR) plans work differently. Your monthly payment is calculated as a percentage of your discretionary income—typically 10% to 20%—not as a function of your loan balance. Under the SAVE plan, payments are capped at 10% of discretionary income for undergraduate loans, and discretionary income is defined as your adjusted gross income (AGI) minus 225% of the federal poverty guideline for your household size.

For our example borrower earning $55,000 as a single filer:

Standard Plan Snapshot

  • Loan: $45,000 at 6.8% over 10 years
  • Monthly payment: approximately $518.36
  • Total paid over 10 years: approximately $62,203
  • Total interest: approximately $17,203

SAVE Plan Snapshot (Year 1)

  • AGI: $55,000
  • 225% of poverty guideline (single, 2024): $33,075
  • Discretionary income: $55,000 minus $33,075 = $21,925
  • 10% of discretionary income: approximately $2,192.50 per year
  • Monthly payment: approximately $182.71

The gap is striking: $518 versus $183 per month. But this is only Year 1. The comparison tool needs to project forward.

How do I calculate monthly payments for each student loan plan?

For the standard plan, the formula is a basic amortization calculation:

M = P × [r(1+r)^n] / [(1+r)^n minus 1]

Where P = $45,000, r = 0.068/12 = 0.00567, and n = 120. This gives M ≈ $518.36. Fixed. Done.

For IDR plans, your comparison tool needs to recalculate annually. Each year, the borrower recertifies their income, and the payment adjusts. This is where most comparison tools fail—they use static Year 1 payments and project them forward for 20 years. That's not how IDR works in practice.

Your tool needs to model income growth. If our borrower starts at $55,000 and sees 4% annual raises, the SAVE payment trajectory looks like this:

  • Year 1: $55,000 salary → payment approximately $183
  • Year 5: $64,283 salary → payment approximately $260
  • Year 10: $78,029 salary → payment approximately $375
  • Year 15: $94,727 salary → payment approximately $514
  • Year 20: $114,942 salary → payment capped at standard amount, approximately $518

Under SAVE, payments cap at the standard 10-year amount when income gets high enough. Once our borrower's salary exceeds roughly $108,000, they'd pay the standard $518—but they'd still be on the hook for any remaining balance at Year 20 forgiveness.

How does salary growth affect income-driven repayment over time?

This is the variable that makes or breaks your comparison tool. A borrower earning $55,000 at age 23 will likely earn far more by age 43. If you model flat income, you'll dramatically overstate the benefits of IDR and mislead the user.

Here's what happens with 4% annual growth under SAVE for our $45,000 borrower:

  • Year 1: salary $55,000, payment $183, cumulative paid $2,196
  • Year 5: salary $64,283, payment $260, cumulative paid approximately $13,180
  • Year 10: salary $78,029, payment $375, cumulative paid approximately $30,420
  • Year 15: salary $94,727, payment $514, cumulative paid approximately $54,600
  • Year 20: salary $114,942, payment $518 (capped), cumulative paid approximately $82,900

Compare that to the standard plan: 120 payments of $518 equals $62,203 total. Under SAVE with 4% growth, our borrower pays roughly $82,900 over 20 years—about $20,700 more than the standard plan. The lower early payments cost them in the long run because the loan balance accrues interest faster than the payments chip away at it.

What is the total interest paid under each repayment plan?

Let's break down interest versus principal for both paths.

Standard Plan (10 Years)

  • Total principal paid: $45,000
  • Total interest paid: approximately $17,203
  • Total cost: approximately $62,203

SAVE Plan (20 Years, 4% Income Growth)

  • Total payments: approximately $82,900
  • Principal portion: approximately $45,000
  • Interest portion: approximately $37,900
  • Forgiven balance at Year 20: minimal or zero, depending on amortization

Under IDR, early payments may not even cover accruing interest. In Year 1, our borrower's $183 monthly payment against a $45,000 balance at 6.8% generates $255 in monthly interest. The SAVE plan subsidizes 50% of unpaid interest for undergraduate loans, but the balance can still grow initially before payments catch up.

This is where your comparison tool needs a proper amortization engine that tracks monthly interest accrual, payment allocation between interest and principal, unpaid interest subsidization under SAVE, and the running balance. A simple multiplication of monthly payment times months remaining won't cut it.

Is student loan forgiveness under IDR worth it?

For our example borrower, forgiveness at Year 20 is unlikely to save them money. Their income grows fast enough that by Year 12, they're paying more per month than the standard amount. The remaining balance at Year 20 would be minimal—possibly zero.

But change the inputs and the story flips completely. If our borrower earns $45,000 with only 2% annual growth:

  • Year 1 payment: approximately $100 per month
  • Year 20 payment: approximately $148 per month
  • Total paid over 20 years: approximately $29,800
  • Remaining balance forgiven: approximately $35,000 or more

Here, IDR clearly wins. The borrower pays less than the original principal, and the forgiven amount is substantial—though potentially taxable as income, depending on current IRS rules and any legislative changes through 2025 and beyond.

Your comparison tool should flag this inflection point. I typically build in a break-even income growth rate calculation—the annual raise percentage at which standard repayment becomes cheaper than IDR. For our $45,000 loan at 6.8% with a $55,000 starting salary, that break-even sits around 3.2%. Below that growth rate, IDR wins. Above it, standard wins.

How do I build a standard vs income-driven repayment comparison tool?

If you're building this tool for a website or app, here's the architecture I'd recommend from having shipped similar calculators.

Core Inputs

  • Loan balance, separated by undergraduate vs. graduate
  • Weighted average interest rate
  • Starting salary and expected annual growth rate
  • Family size (affects poverty guideline calculation)
  • State of residence (affects poverty guideline in some plans)
  • Tax filing status (single, married filing jointly, married filing separately)

Calculation Engine

Build two parallel amortization schedules. The standard path is straightforward: fixed payment over 120 months. The IDR path requires annual recalculation based on projected AGI, with the payment capped at the standard amount. You need to track unpaid interest, apply the SAVE subsidy for undergraduate loans, and check for forgiveness at 20 or 25 years depending on the plan and loan type.

Output Metrics

  • Total paid under each plan
  • Total interest versus principal breakdown
  • Monthly payment trajectory—chart this, because users need to see the curve visually
  • Forgiveness amount if any, plus estimated tax liability on forgiven balance
  • Break-even income growth rate

What edge cases should my student loan comparison calculator handle?

Every comparison tool I've built has uncovered edge cases that break naive calculations. Here are the ones that matter most:

Negative amortization: When IDR payments don't cover accruing interest, the balance grows. Under SAVE, 50% of unpaid interest is subsidized for undergraduate loans, but you still need to track the remaining 50% and model its impact on the balance over time.

Income interruptions: If a borrower loses their job or drops to part-time, IDR payments can drop to $0. Your tool should allow users to model income interruptions at specific years, not just smooth growth curves.

Marriage and filing status: Filing jointly versus separately changes the AGI used for IDR calculations. A spouse's income can double the discretionary income figure, dramatically raising the IDR payment. This alone can swing the comparison from IDR-favorable to standard-favorable.

Plan switching: Borrowers can switch from IDR to standard and back. Each switch can reset the amortization clock or trigger interest capitalization. Your tool should at minimum note this as a limitation if you can't model it dynamically.

Public Service Loan Forgiveness (PSLF): If the borrower works in qualifying public service, forgiveness comes at 10 years tax-free. This completely changes the math. For our example borrower under SAVE with PSLF, they'd make 10 years of lower payments averaging roughly $280 per month—totaling about $33,600—and then the remaining balance is forgiven tax-free. That beats the standard plan's $62,203 by nearly $29,000. PSLF should be a toggle in your tool, not an afterthought.

For our example borrower without PSLF—$45,000 at 6.8%, $55,000 starting salary, 4% growth—the standard 10-year plan is the better financial choice. They'll pay $62,203 total versus roughly $82,900 under SAVE. But flip the PSLF switch, or drop the growth rate to 2%, and SAVE becomes the clear winner. The right comparison tool doesn't just calculate—it surfaces these decision points so the borrower understands exactly what they're choosing between and why.