Loan Calculator
Estimate the monthly payment, total interest and full cost of any fixed-rate loan — personal, auto or mortgage.
Anyone with the link can see the numbers included in it.
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Last reviewed: July 20, 2026 · Formulas verified by automated tests before every release.
Compare two loans side by side
The classic dilemma — a longer term with a smaller payment, or a shorter one that costs less overall — stops being abstract when both columns sit next to each other. Try 5 vs 3 years on the same amount: the Δ column shows exactly what the comfortable payment costs in extra interest, and the verdict says it in one sentence. Comparing offers from two banks works the same way: same amount and term, different rates — the table shows what that 0.5% is really worth. Use "Copy link with my numbers" to send the whole comparison to whoever shares the decision.
How loan payments work
A fixed-rate loan is repaid in equal monthly installments. Early payments are mostly interest; later payments are mostly principal — this schedule is called amortization. The calculator applies the standard formula used by banks worldwide:
M = P × r × (1 + r)ⁿ ÷ ((1 + r)ⁿ − 1)
P — loan amount · r — monthly rate (annual ÷ 12) · n — months
Example
Borrowing $20,000 at 7.5% for 5 years gives a monthly payment of about $400.76. Over 60 payments you repay roughly $24,046 — meaning the loan costs about $4,046 in interest. The same loan over 3 years raises the payment to about $622 but cuts total interest to roughly $2,398.
Disclaimer
This tool provides estimates for information purposes only and is not financial advice. Actual offers include fees, insurance and rate conditions that vary by lender — always check the full loan agreement before signing.
Sources, assumptions and limitations
- Formula: M = P × r(1+r)ⁿ ÷ ((1+r)ⁿ − 1), monthly rate r = annual ÷ 12; total interest = M × n − P
- Assumptions: Fixed-rate, fully amortizing loan; equal monthly payments; interest compounds monthly. No external data used — pure arithmetic on your inputs.
- Not included: Origination and processing fees, insurance, APR vs nominal rate differences, variable-rate scenarios, early-repayment penalties.
- Last reviewed: July 22, 2026 by the CalcNotebook team
Frequently asked questions
How do I compare two loan offers side by side?
Tap "Compare two scenarios": enter both offers (amount, rate, term) and get a table of monthly payment, total paid and total interest with the difference for each row — plus a plain-language verdict on which costs less overall and which is easier monthly.
How is the monthly loan payment calculated?
The calculator uses the standard amortization formula: M = P × r × (1 + r)ⁿ ÷ ((1 + r)ⁿ − 1), where P is the loan amount, r the monthly interest rate and n the number of monthly payments.
What is total interest?
Total interest is everything you pay on top of the amount you borrowed: monthly payment × number of payments − loan amount. Shorter terms mean higher monthly payments but far less total interest.
Does this work for mortgages and car loans?
Yes — any fixed-rate, fully amortized loan follows the same math. It does not model variable rates, interest-only periods, fees or insurance, so treat the result as an estimate.
How can I reduce the total cost of a loan?
Three levers matter most: a lower interest rate (shop around and improve your credit score), a shorter term, and extra principal payments — even small ones early in the loan cut interest significantly.