A transparent look at the formulas, data sources, and validation processes behind every DegreeCalc education calculator.
The College Cost Calculator projects total cost of attendance using NCES IPEDS data and historical tuition inflation rates:
Annual Cost of Attendance = Tuition + Fees + Room & Board + Books + Personal Expenses
Projected Cost (Year N) = Current Cost x (1 + Inflation Rate)^N
Historical tuition inflation: ~3.5% (public) to ~3.0% (private) annually
Total 4-Year Cost = Sum of Projected Cost for Years 1 through 4
Net Cost = Total Cost - Grants - Scholarships - Financial Aid
Our College Comparison tool uses the same projection method to let users compare total costs across institutions, factoring in different tuition rates, aid packages, and living costs.
The Student Loan Calculator and Loan Repayment Calculator implement standard amortization formulas:
Monthly Payment = P x [r(1+r)^n] / [(1+r)^n - 1]
Where: P = Principal, r = Monthly interest rate, n = Total payments
Total Interest = (Monthly Payment x n) - P
2026 Federal Student Loan Rates:
Direct Subsidized/Unsubsidized (Undergraduate): 6.53%
Direct Unsubsidized (Graduate): 8.08%
Direct PLUS: 9.08%
Income-Driven Repayment (IDR):
SAVE Plan: 5% of discretionary income (undergrad)
IBR: 10-15% of discretionary income
Discretionary Income = AGI - 225% of Federal Poverty Level
The calculator supports all federal repayment plans including Standard (10-year), Extended, Graduated, and income-driven options. It shows total interest paid, loan forgiveness eligibility timeline, and payment comparisons across plans.
The Degree ROI Calculator and Graduate School ROI Calculator use net present value (NPV) methodology:
Earnings Premium = Degree Holder Median Earnings - HS Diploma Median Earnings
Annual Net Benefit = Earnings Premium - Annual Loan Payment
NPV = Sum of [Annual Net Benefit / (1 + discount_rate)^year] for career years
minus Total Education Cost
Simple ROI = (Lifetime Earnings Premium - Total Cost) / Total Cost x 100
Payback Period = Total Cost / Annual Earnings Premium
BLS Median Earnings by Education (2025):
High School Diploma: $42,068/year
Bachelor's Degree: $69,368/year
Master's Degree: $81,848/year
Professional Degree: $100,048/year
The discount rate defaults to 3% (real rate, inflation-adjusted) but is user-configurable. Earnings data comes from BLS Current Population Survey median weekly earnings by education level.
The GPA Calculator supports both unweighted (4.0 scale) and weighted GPA systems:
Unweighted GPA (4.0 Scale):
A/A+ = 4.0 | A- = 3.7 | B+ = 3.3 | B = 3.0 | B- = 2.7
C+ = 2.3 | C = 2.0 | C- = 1.7 | D+ = 1.3 | D = 1.0 | F = 0.0
GPA = Sum of (Grade Points x Credit Hours) / Total Credit Hours
Weighted GPA (5.0/6.0 Scale):
Honors: +0.5 to grade points
AP/IB: +1.0 to grade points
Cumulative GPA = Sum of (All Semester Quality Points) / Total Credit Hours
The Credit Calculator helps students track credit hours toward graduation requirements, accounting for transfer credits and AP/IB exam scores.
The FAFSA EFC Calculator follows the federal EFC formula methodology:
Parent Contribution = (Adjusted Available Income x Assessment Rate)
/ Number of Family Members in College
Student Contribution = (Student Income above allowance x 50%)
+ (Student Assets x 20%)
EFC = Parent Contribution + Student Contribution
Key Parameters:
Income Protection Allowance: Varies by family size
Asset Protection Allowance: Based on older parent age
Parent asset assessment rate: 5.64% (max)
Student asset assessment rate: 20%
Note: The FAFSA Simplification Act replaced EFC with the Student Aid Index (SAI) starting with the 2024-25 award year. Our calculator reflects the current SAI methodology while maintaining backward compatibility for comparison purposes.
The College Savings Calculator uses compound interest with regular contributions:
Future Value = P x (1 + r)^n + PMT x [((1 + r)^n - 1) / r]
Where: P = Initial balance, r = Monthly return, n = Months, PMT = Monthly contribution
Savings Gap = Projected College Cost - Future Value of Savings
Required Monthly Savings = Gap x [r / ((1 + r)^n - 1)]
Default assumptions:
529 Plan return: 6% annual (balanced portfolio)
Tuition inflation: 3.5% annual