How this works
Most installment loans — personal, auto, student, business — use the same formula your bank does: a fixed monthly payment that pays off both interest and principal over a set number of months. Early payments are mostly interest; later ones are mostly principal. Plug in the loan amount, the annual rate, and the term in years to see your payment, the total interest you'll pay, and the total cost over the life of the loan.
The single biggest factor that determines your rate isn't the loan amount or the term — it's whether the loan is secured or unsecured. A secured loan is backed by a specific asset the lender can repossess if you default: the house in a mortgage, the car in an auto loan, the deposit in a HELOC. Because the lender's risk is lower, secured loans get the lowest rates (typically 5–9% in the current US market). An unsecured loan has no collateral — the lender only has your promise and your credit history — so they price in the higher default risk: typical personal loan APRs run 8–25% for prime borrowers and 25–36% for subprime. Credit cards (a form of unsecured revolving credit) sit at the top of the range, often 20–30% even for good credit.
The right loan type depends on the use. Personal loans (typically $1,000–$50,000, 2–7 year terms) are flexible and unsecured — best for debt consolidation, medical bills, or one-off home repairs. Auto loans are secured by the car and have lower rates than personal loans, but tie you to a specific vehicle. Student loans (especially US federal ones) carry below-market rates and flexible repayment options that no other loan type matches; never refinance federal loans into private without understanding what you're giving up. Business loans split into SBA loans (government-backed, longer terms, lower rates), term loans (lump sum, fixed rate), and lines of credit (revolving, like a credit card). Avoid payday loans and title loans entirely — APRs of 200–400% are typical and the structure is designed to roll over.
The formula
M = monthly payment. P = principal (loan amount). r = monthly interest rate (annual rate ÷ 12, as a decimal — 7.5% → 0.00625). n = total number of payments (years × 12).
Example calculation
- You borrow $25,000 at 7.5% annual interest over 5 years (60 monthly payments).
- Monthly rate r = 7.5 / 100 / 12 = 0.00625. Number of payments n = 60.
- Monthly payment ≈ $501. Total paid ≈ $30,065. Total interest ≈ $5,065.
Frequently asked questions
Does this work for any loan type?
Yes for any fixed-rate amortizing loan: personal loans, auto loans, student loans, small-business loans, even mortgages (use our dedicated mortgage calculator if you also want tax and insurance). It does not handle variable-rate loans or interest-only periods.
How much can extra payments save me?
Often a lot — every extra dollar goes straight to principal, which means less interest in every future month. On a 5-year, $25k loan at 7.5%, paying just $50 extra a month finishes the loan ~10 months early and saves around $500 in interest. Check your loan agreement for prepayment penalties first.
Why is the total interest so much higher than I expected?
Because the rate is annual but applies every year. A 5-year loan at 7.5% doesn't cost 7.5% — it costs roughly 7.5% × 5 / 2 of the loan amount in total interest (the / 2 because the balance shrinks over time). Longer terms make the gap between "rate" and "total interest" much wider.
Should I pick a shorter or longer term?
Shorter terms mean higher monthly payments but much less total interest. Longer terms mean lower monthly payments but more total interest and a higher chance of being upside-down (owing more than the asset is worth) on auto loans. Pick the shortest term whose monthly payment fits your budget with breathing room.
What's the difference between a secured and an unsecured loan?
A secured loan is backed by collateral — a specific asset the lender can seize if you stop paying. Mortgages (house), auto loans (car), and home-equity lines (house equity) are all secured. Because the lender's risk is lower, rates are too: typically 5–9% in current US conditions for prime borrowers. Unsecured loans — personal loans, credit cards, most student loans — have no collateral, just your promise and credit history. Lenders price in default risk, so APRs run 8–25% for prime borrowers and 25–36% for subprime. Practically: if you can secure the loan with an asset (and accept the risk of losing it), you'll save thousands in interest. If not, focus on getting the best unsecured rate by improving your credit score and shopping at least 3 lenders.
What's a reasonable APR for a personal loan?
Depends on your credit and the lending environment, but here are current US benchmarks (2026 averages from LendingTree, Bankrate, and Federal Reserve data). Excellent credit (FICO 720+): 7–12% APR. Good credit (660–719): 13–18%. Fair credit (580–659): 19–25%. Bad credit (<580): 25–36% — and at the upper end, you should ask whether borrowing is worth it. Always compare APR (not just interest rate) — APR includes origination fees, which can add 1–8% to the effective cost. Online lenders (SoFi, LightStream, Upgrade, Discover) typically beat traditional banks by 1–3 points; credit unions can be even lower if you qualify for membership.
What hidden fees should I watch for?
Four to check before signing. (1) Origination fee — typically 1–8% of the loan amount, deducted from the funds you receive. A $20,000 loan with a 5% origination fee delivers $19,000 but you owe interest on the full $20,000. The APR captures this; the headline 'rate' usually doesn't. (2) Prepayment penalty — most US personal loans don't have one anymore, but some still do, especially auto and mortgage loans. Check the contract for 'prepayment penalty' or 'prepayment fee'. (3) Late-payment fees — usually $25–$40 or 5% of the missed payment. They also can trigger a credit-score hit if late by 30+ days. (4) Returned-payment fees if a direct debit fails — typically $25–$35. None of these are catastrophic individually, but together they can shift a 'great rate' loan into a mediocre one. The APR figure is your best single-number comparison; ask the lender for a Loan Estimate or Truth-in-Lending Disclosure that itemises every fee.