Loan Calculator (monthly payment, interest, total cost)
Enter the loan principal, annual interest rate, and term in years to see the monthly payment, total amount paid, and total interest. Works for mortgages, car loans, student loans, and personal loans.
- Monthly payment
- $1,266.71
- Total paid
- $456,017
- Total interest
- $206,017
How it works
How fixed-rate loans work
A fixed-rate loan has a constant monthly payment that pays off both principal and interest over the term. The standard formula is M = P × r / (1 − (1 + r)^−n), where P is the principal, r is the monthly interest rate (annual rate / 12), and n is the total number of payments (years × 12). At a 4.5% rate over 30 years, a $250,000 mortgage costs about $1,267/month.
Each monthly payment is split between interest and principal. Early payments are mostly interest; later payments are mostly principal. This is why making extra payments early in the term has an outsized effect on total interest paid — you're cutting the principal that future interest is calculated on.
What this calculator does and doesn't include
Included: principal repayment and interest. The monthly figure is the principal-and-interest portion only.
Not included for mortgages: property tax, homeowners insurance, mortgage insurance (PMI), and HOA fees. These can add 20-40% to the actual housing payment in many US markets. Always check the lender's full disclosure before assuming the calculator's monthly figure is your real cost.
Not included for car loans: sales tax, registration, gap insurance. Many US states tax vehicles at purchase; the loan principal you enter should usually be after-tax for accurate monthly numbers.
How rate and term affect total cost
On a $250,000 mortgage at 4.5%, going from 30 to 15 years roughly doubles the monthly payment ($1,267 → $1,912) but cuts total interest from $206,000 to $94,000 — a $112,000 lifetime savings. Higher monthly, much lower total.
Going from 4.5% to 6.5% on the same 30-year mortgage raises the monthly to $1,580 and increases total interest from $206,000 to $319,000. A 2 percentage-point rate change roughly increases total cost by 50%. This is why locking a rate matters.
Frequently asked questions
›Why doesn't the monthly include taxes and insurance?
Because those vary widely by location, lender, and individual. The 'principal and interest' (P&I) figure is universal; add your local taxes and insurance separately.
›What's the difference between APR and interest rate?
Interest rate is the cost of the money. APR includes the rate plus fees expressed annually. Use the interest rate for monthly payment math; use APR to compare loan offers.
›How do extra payments affect the loan?
Each extra dollar applied to principal saves multiple dollars of future interest. Online amortization tables can show the new payoff date.
›Should I take a 15-year or 30-year mortgage?
15-year saves a lot of interest and builds equity faster. 30-year has lower monthly payments and more flexibility. Choose based on your monthly cash flow and other investment options.
›What's the difference between simple and compound interest?
Mortgages, auto, and personal loans use simple monthly interest (no compounding within the month). Credit cards compound daily, which is why they're more expensive than the headline APR suggests.
›Why is early payment mostly interest?
At month 1, the entire principal accrues interest. As principal shrinks, less interest accrues, so more of each fixed payment goes to principal.
›Does the calculator handle adjustable-rate loans?
Not directly — it assumes a fixed rate. For ARMs, run the calculator at the initial rate and again at the assumed reset rate to see the range.
›Is the data sent anywhere?
No. All math runs in your browser.
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