Loan laboratory: select among payment, future value, and present value
Use amortized mode when a borrower repays principal and interest through equal installments. Use deferred-payment mode when one starting principal grows to a single maturity value. Use bond mode when the future maturity amount is known and the question is its present value at an entered yield convention. These are different timelines and directions of calculation. Selecting a mode by the word “loan” rather than by contractual cash flows can produce a polished but meaningless answer, so sketch the dates and arrows before entering numbers.
Loan laboratory: convert mismatched frequencies transparently
Discrete growth uses the selected compounding frequency, while continuous mode uses exponential growth. When amortized payments occur on a different schedule from compounding, the model converts the entered nominal rate to an equivalent rate for each payment period before solving the annuity. That conversion is not the same as simply dividing by the number of payments. Compare a conventional monthly table with the Amortization Calculator and use the Compute Interest Calculator only when its simple-or-compound growth task matches the agreement.
Loan laboratory: keep extra principal and origination fees in their lanes
In amortized mode, an optional extra amount is applied after each period's interest, reducing principal and potentially shortening the schedule. An entered origination fee appears in total cost and net proceeds; it is not silently added to principal. That distinction preserves both the contractual balance and cash received. Use the Vehicle Refinance Calculator when an auto-loan task starts from a current balance and a documented replacement offer, or the APR Calculator when finance charges must be tested as annualized cash-flow costs.
Loan laboratory: reproduce the audited $100,000 vectors
With $100,000 over ten years at 6%, monthly compounding and monthly repayment produce a $1,110.21 amortized payment and $33,224.60 total interest. With annual compounding, the same $100,000 starting principal grows to $179,084.77 in deferred mode. Reversing direction, a $100,000 maturity amount discounted ten years at the same annual rate has a $55,839.48 present value in bond mode. These tested reference examples establish behavior; they are not market quotes or claims about an available security.
Loan laboratory: stop where fixed-rate mathematics stops
The schedules retain unrounded periodic values and round money for display, but precision cannot cure a wrong contract model. Variable indices, option payments, default interest, day-count conventions, taxes, security prices, call features, and lender underwriting require additional evidence. Compare the result with the written note or offering materials and preserve frequency definitions. This is a fixed-scenario mathematics tool, not a lender quotation, securities valuation opinion, tax analysis, or recommendation to borrow, invest, refinance, or prepay.