Monthly payment and total interest on a fixed-rate personal loan

What a Personal Loan Actually Costs

Personal loans are fixed-rate, fixed-term loans used for debt consolidation, major purchases, or unexpected expenses. The headline number most people see is the monthly payment, but the total interest over the loan's life usually matters more. A 15,000 loan at 10% APR over 36 months has a 484 monthly payment and 2,415 total interest. Stretch to 60 months and monthly drops to 319 — comforting — while total interest balloons to 4,122, a 70% increase in real cost. This calculator shows both so the real trade-off is visible.

How the Amortisation Math Works

Every payment is split between interest (on the remaining balance) and principal (reducing that balance). Early payments are mostly interest because the balance is high. Late payments are mostly principal because the balance has shrunk. The standard formula M = P × r / (1 - (1+r)^-n) produces a constant monthly payment where the internal split shifts over time. Amortisation schedules reveal that a 60-month loan pays roughly 75% interest in the first 12 months and 25% in the last 12, even though the total monthly stays flat.

Realistic Rates by Credit Profile

Excellent credit (740+): 6-9% APR on unsecured personal loans. Good credit (670-739): 9-13%. Fair credit (580-669): 15-22%. Below 580: 22-36% or declined. Credit unions and online lenders (SoFi, Upgrade, Marcus, LightStream) often beat traditional bank rates by 1-3 percentage points for similar credit profiles. Secured loans (against a car, savings account, or home equity) drop rates 2-5 points versus unsecured. Shop at least 3 lenders before committing.

Term Length Trade-Offs

Shorter term (24-36 months): higher monthly payment, much lower total interest. Best when cash flow supports it. Longer term (60-84 months): lower monthly, higher total interest. Can make sense for cash-flow constrained households if the alternative is unaffordable monthly payment that forces the loan to default. Never extend term just for comfort — run the calculator to see the real interest cost, then decide whether the cash flow gain justifies it.

Worked Example

15,000 principal, 10% APR, 36-month term. Monthly rate: 10/100/12 = 0.833%. Monthly payment: 484. Total paid: 17,411. Total interest: 2,411. Interest as percentage of principal: 16.1%. Compare same loan at 48 months: monthly drops to 380, total paid 18,250, total interest 3,250 (21.7% of principal). Compare at 60 months: monthly 319, total paid 19,122, total interest 4,122 (27.5% of principal). The first 2 years of term-stretching add 1,711 of interest; extending from 48 to 60 adds another 872. Every extra year costs real money.

What This Calculator Does Not Model

Origination fees (1-8% of loan amount, deducted from disbursement or added to principal). Late payment fees. Prepayment penalties (uncommon but exist on some loans — check the contract). Variable-rate personal loans where the rate can change during the term. Autopay discounts (0.25% typical). Balance transfer fees if using a balance-transfer credit card as an alternative. For a more complete picture, use the debt-consolidation-calculator to compare this option against alternatives.

When a Personal Loan Beats a Credit Card

Carrying a 15,000 balance on a 22% APR credit card making minimum payments takes 8+ years to clear and costs over 15,000 in interest. Consolidating that balance into a 10% personal loan with a fixed 36-month term caps the term at 3 years and cuts interest to about 2,400 — savings over 12,000. This is the most common and financially sound use of personal loans. Avoid using them to fund discretionary spending you cannot afford otherwise; use them to replace more expensive debt or fund genuine necessities.