Loan Calculator
Monthly payment, total interest, and full amortization for any loan — personal, student, RV, business, or other. With extra-payment what-ifs.
Payment per month
| # | Interest | Principal | Balance |
|---|---|---|---|
| 1 | $116.67 | $279.36 | $19,720.64 |
| 2 | $115.04 | $280.99 | $19,439.66 |
| 3 | $113.40 | $282.63 | $19,157.03 |
| 4 | $111.75 | $284.27 | $18,872.76 |
| 5 | $110.09 | $285.93 | $18,586.82 |
| 6 | $108.42 | $287.60 | $18,299.22 |
| 7 | $106.75 | $289.28 | $18,009.94 |
| 8 | $105.06 | $290.97 | $17,718.98 |
| 9 | $103.36 | $292.66 | $17,426.31 |
| 10 | $101.65 | $294.37 | $17,131.94 |
| 11 | $99.94 | $296.09 | $16,835.86 |
| 12 | $98.21 | $297.81 | $16,538.04 |
How a loan payment is calculated
Most US consumer loans use a fixed-payment, fully-amortizing schedule: the same payment every period, with each payment split between interest (calculated on the remaining balance) and principal (the rest). Early payments are mostly interest; later payments are mostly principal. This calculator handles personal loans, student loans, business loans, RV/boat loans, and any other fixed-rate installment debt.
APR vs interest rate — the lender's honest number
Interest rate is what you pay on the principal balance. APR(Annual Percentage Rate) bakes in interest plus any origination fees, points, or required charges, amortized over the loan term. APR is the better comparison number when shopping multiple lenders.
Truth-in-lending laws require US lenders to disclose APR. If two lenders quote you 7% and 7.5% on the same loan, but lender A has a 2% origination fee and lender B has none, lender B might actually be cheaper. Always compare APR-to-APR.
Loan types you can model with this calculator
- Personal loans — typical rates 8–24% APR, terms 2–7 years. Good for debt consolidation, home repairs, medical bills.
- Student loans — federal subsidized/unsubsidized rates set by Congress. Private student loans range 4–14% APR. Terms typically 10–25 years.
- RV / boat loans — secured by the vehicle. Rates 6–12% APR, terms 5–20 years.
- Small business loans — wide variation. SBA loans 6–10%, online lenders 8–35%, term loans 1–10 years.
- Medical loans — typically personal loans repurposed. Watch for high APRs from healthcare-specific lenders.
For specific common loans, we have dedicated calculators with extra detail: Mortgage Calculator for home loans (with PITI), Auto Loan Calculator for car loans (with state sales tax).
The case for extra principal payments
Almost every US consumer loan allows prepayment without penalty (a few specialty mortgages and some commercial loans don't — check your loan docs). Extra principal payments are essentially a guaranteed return equal to your loan's interest rate, tax-free.
Concrete: a $20,000 personal loan at 9% APR over 5 years has a $415/month payment and $4,910 in total interest. Adding just $50/month extra ($465 total) shortens the term to ~4 years and saves ~$1,100 in interest. The math works the same for any fixed-rate loan.
Caveat: only do this after you have an emergency fund and any high-interest credit-card debt is gone. A 9% loan beats a 4% savings account, but credit-card debt at 22%+ APR beats both.
Picking a loan term
Shorter terms = higher monthly payments but dramatically less total interest. A $20,000 loan at 8%:
- 3 years: $626/month, $2,544 total interest
- 5 years: $406/month, $4,332 total interest
- 7 years: $312/month, $6,201 total interest
Pick the shortest term where the payment fits your budget with comfortable margin. Don't stretch the term to maximize the loan amount — that's how people end up upside-down (owing more than the asset is worth).
Variable vs fixed rates
This calculator assumes a fixed rate. Variable-rate loans (some private student loans, HELOCs, some personal loans) reset periodically based on a benchmark like SOFR or Prime. If rates rise, your payment rises. Run scenarios at a higher rate (your current rate + 2–3%) to stress-test affordability before signing a variable loan.