Student Loan Repayment ToolOld Income-Based Repayment (IBR)
Old Income-Based Repayment (IBR)
Calculator
Estimate your monthly payment under the original IBR formula using your loan balance, income, and family size.
Calculate Your IBR Payment Now →How It Works
How to Use This Calculator
The Old Income-Based Repayment (IBR) plan calculates your payment based on 15% of your discretionary income, but never more than what you would pay under a standard 10-year repayment plan.
- 1Enter your total eligible loan balance — your principal when you entered repayment.
- 2Enter your average annual interest rate. It converts automatically to a monthly rate.
- 3Enter your Adjusted Gross Income (AGI). If married, include combined income.
- 4Select your filing status and number of dependents to determine family size.
- 5Choose your state of residence — poverty guidelines vary by location.
- 6Click “Calculate Payment” to see your estimated Old IBR monthly payment.
How Poverty Guideline (PL) is determined:
The calculator uses federal poverty guideline tables based on state and family size. 150% of this amount is subtracted from AGI to determine discretionary income.
The calculator uses federal poverty guideline tables based on state and family size. 150% of this amount is subtracted from AGI to determine discretionary income.
Calculate Your IBR Payment
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The Math Behind It
How Your Old IBR Payment is Calculated
Your Old Income-Based Repayment (IBR) payment is determined using three core formulas.
1. Standard 10-Year Repayment Cap (S)
This is the maximum monthly payment you would make under a fully amortized 10-year repayment plan. Your IBR payment can never exceed this amount.
S = P × r(1 + r)120(1 + r)120 − 1
- P = Loan principal balance at repayment start
- r = Monthly interest rate = (Annual Rate ÷ 100 ÷ 12)
- 120 = 10 years × 12 months
- This is the standard amortization formula used for installment loans
2. Discretionary Income (Dinc)
Discretionary income equals your income above 150% of the federal poverty guideline.
Dinc = MAX(0, AGI − (1.5 × PL))
- AGI = Adjusted Gross Income (Combined if Married; Individual if Single)
- PL = HHS Poverty Guideline for the borrower’s family size and state of residence
- 1.5 × PL = 150% poverty protection threshold
- If AGI is below 150% of PL, discretionary income is $0
3. Final Monthly Payment (M)
Your required monthly payment is the lesser of:
- 15% of discretionary income (converted to monthly)
- The standard 10-year repayment cap (S)
M = MAX(0, MIN(0.15 × Dinc12, S))
- 0.15 = 15% required under Old IBR
- Division by 12 converts annual income to monthly amount
- Payment cannot exceed S
- If calculated payment is less than $5 → payment becomes $0
- If payment is between $5 and $10 → payment becomes $10
