Student Loan Calculator

What this calculator does

A student loan structured as a fixed-rate, fixed-term instalment loan amortises in the same way as any other amortising loan: a constant monthly payment splits between interest on the remaining balance and principal repayment, and the balance clears at the end of the term. This calculator takes three inputs — loan balance, annual interest rate, and repayment term in years — and returns the monthly payment, total interest paid across the term, and total amount paid. The math is the standard amortisation formula used for personal loans, mortgages, and any other fully-amortising fixed-rate loan.

The amortisation math

The monthly payment is M = P × r ÷ (1 − (1 + r)⁻ⁿ), where P is the loan balance, r is the monthly rate (annual rate ÷ 12, expressed as a decimal), and n is the number of monthly payments (term in years × 12). Total paid is M × n. Total interest is total paid minus the original loan balance. Each monthly payment splits between interest on the remaining balance and principal repayment; early payments are mostly interest because the balance is large, and later payments are mostly principal as the balance falls. The constant monthly figure masks this internal shift.

Worked example

Take a 35,000 student loan at 6% annual rate over a 10-year term. The monthly rate is 6 ÷ 12 = 0.5%. The standard formula produces a monthly payment of about 388.57. Total paid across 120 months is approximately 46,628.57. Total interest is 46,628.57 − 35,000 = 11,628.57, which is about 33% of the original balance. Stretching the term to 20 years at the same rate drops the monthly payment to about 250.75 but raises total interest to about 25,180 — more than double the 10-year figure.

The term-length trade-off

A shorter term raises the monthly payment but cuts the total interest paid. A longer term does the opposite: lower monthly figure, higher total interest paid across the longer life. The trade-off depends on what is constraining the borrower — if cash flow has slack, a shorter term saves money on the total cost; if cash flow is tight, a longer term may keep payments affordable enough to avoid late or missed payments. The calculator surfaces both the monthly figure and total interest so the trade-off is explicit at the inputs entered.

What this calculator does not model

Income-contingent repayment systems exist in several jurisdictions where the monthly payment is computed from the borrower's income above a threshold rather than from amortisation. Examples include the United Kingdom Plan 1/2/4/5 system and various income-driven plans in other markets. Under those structures, the monthly figure depends on earnings, the term is open-ended (with a write-off after a fixed number of years), and total cost can vary widely across borrowers with the same nominal balance. This calculator does not model any of those systems — it assumes a fixed monthly payment under standard amortisation. For income-contingent scenarios, the calculator output is not directly applicable; refer to the loan servicer or the relevant programme rules for projections under those rules.

The calculator also does not capture origination or arrangement fees (sometimes deducted from disbursement or added to principal), capitalised interest accrued during deferment or grace periods, late-payment fees, prepayment provisions, autopay or relationship discounts, or variable-rate loans where the rate moves during the term.

How to read the output

The monthly figure is the cash-flow line: how much will leave the account each month under standard amortisation. The total-interest figure is the planning line: how much the loan will cost overall, against which alternatives can be compared. The total-paid figure is the gross outflow across the full term. Together they capture the cost picture for a fixed-rate, fixed-term student loan in any market that uses an amortising structure.