How to compare a loan payment with compound interest
When to amortize a debt versus projecting a deposit, with the formulas Toolora uses in the browser.
Amortization shrinks a balance
A fixed-rate consumer loan splits each monthly payment into interest on the remaining principal and a principal reduction. Toolora estimates the payment with M = P r / (1 − (1+r)^−n), where r is APR/12/100 and n is round(years × 12). If APR is 0, M is simply P/n. Example: 25,000 at 6.5% for 5 years is 60 payments. The page also shows total paid (n × M) and total interest (total paid − P). This is not a bank quote: lenders add origination fees, insurance, taxes, and day-count conventions. Extra principal and biweekly plans change the path. Treat the number as a planning estimate and confirm with a lender.
Compounding grows a deposit
Compound Interest Calculator uses A = P (1 + r/n)^(n t). Interest earned is A − P. Choose n = 1 (annual), 2, 4, 12 (monthly), or 365 (daily). Monthly compounding is common for savings; more frequent n grows slightly faster at the same nominal rate. Example: 10,000 at 5% for 10 years compounded monthly is a textbook future-value problem — there are no recurring deposits, withdrawals, fees, or taxes in the model. Advertised APY already folds compounding into one yearly percent; do not paste APY into the nominal rate field unless you mean to.
Do not mix the two formulas
Borrowing uses amortization; saving uses compound interest. Putting a loan principal into the compound tool answers “what if this were a deposit,” not “what will I pay monthly.” Putting a savings balance into the loan tool invents a payment that does not exist. Currency is a bare number with no FX. Extreme n and t can overflow ordinary floating point — keep inputs realistic.
Privacy and next steps
Both calculators run in the browser. Nothing is uploaded. Related pages: Percentage Calculator for a generic percent-of check, Profit Margin when pricing a product rather than a loan, Discount Calculator for percent-off list prices. After you have a monthly payment, compare it with take-home pay on paper; the site does not budget for you.