How Much Interest You Pay on a $30,000 10-Year Loan

The table below shows the monthly payment and total interest paid on a $30,000 loan over a 10-year term, across a range of APRs from 5% to 10%. This data reveals how small shifts in interest rate directly impact monthly obligations and overall borrowing costs—critical for borrowers considering personal or student loan refinancing.

How APR Affects Monthly Payments and Total Interest

A $30,000 loan over 10 years is a common scenario for refinancing student debt or consolidating personal loans. The table shows that even a modest increase in APR—from 5% to 10%—can significantly raise both monthly payments and total interest paid. At 5%, the monthly payment is $299.74, and total interest over the term is $3,988. At 10%, the monthly payment jumps to $344.32, with total interest climbing to $11,036. That’s an almost 175% increase in interest costs over just five percentage points. This highlights a key trade-off: lower APRs reduce long-term financial strain, but borrowers must weigh this against creditworthiness and market conditions. For instance, a borrower with strong credit and stable income might qualify for the lower end of the range, while someone with a weaker profile may face rates near the upper limit—making the total cost of borrowing substantially higher.

When Does This Scenario Make Financial Sense?

A 5% to -10% APR range is typical for private personal loans and student loan refinancing today. Borrowers should consider this range when evaluating whether to refinance. If the original student loan rate was above 5%, refinancing at 5% could save thousands in interest. But if the original rate was already below 5%, or if the borrower has poor credit, the new rate may be higher—making refinancing less attractive. Moreover, this scenario assumes no loan fees or prepayment penalties. In reality, some lenders charge origination fees or require a minimum credit score. These costs can further erode savings. Borrowers should also consider that lower APRs are more likely when credit scores are strong and income is stable—factors that are not captured in the table but are essential in real-world decisions.

What the Data Shows About Borrowing Costs

The table reveals a non-linear relationship between APR and cost. While the monthly payment increases steadily with APR, the total interest grows at an accelerating rate. This is because interest compounds over time—each month’s interest is calculated on the remaining balance. A higher rate means more interest is charged each month, and that amount accumulates over 120 months. For example, at 5%, the borrower pays $3,988 in interest—just over 13% of the original loan amount. At 10%, that climbs to $11,036—nearly 37% of the principal. This difference underscores why even small rate increases can dramatically affect lifetime costs.

How We Calculated This

The monthly payment and total interest were calculated using the standard amortization formula: **M = P [ r(1+r)^n ] / [ (1+r)^n – 1 ]** Where: - M = monthly payment - P = loan principal ($30,000) - r = monthly interest rate (APR ÷ 12 ÷ 100) - n = number of payments (10 years × 12 = 120) Total interest is then calculated as (monthly payment × number of payments) minus the original loan amount. The data in the table reflects only the interest component, excluding fees or other costs. It represents a pure interest-cost analysis, showing how APR directly shapes borrowing outcomes.

$30,000 loan over 10 years — monthly payment and total interest by APR

APR	Monthly Payment	Total Interest	Total Repaid
5%	$318	$8,184	$38,184
7%	$348	$11,799	$41,799
9%	$380	$15,603	$45,603
11%	$413	$19,590	$49,590