THE NUMORIX GUIDE
How to use the Loan calculator
Last reviewed September 14, 2026
What this calculator does
The amortized mode first converts the nominal annual rate into an effective rate for the selected compounding and payback frequencies.
Formula and method
The amortized mode first converts the nominal annual rate into an effective rate for the selected compounding and payback frequencies. It then uses P = Lr(1+r)^n / ((1+r)^n - 1), where L is the amount, r is the rate per payment period, and n is the rounded count of payments. The schedule applies interest to the opening balance and the remainder of each payment to principal. Deferred mode adds the scheduled interest to principal; the bond panel is a display derived from that same schedule rather than a separate market-bond model.
Variables and inputs
Enter the amount or predetermined due amount in dollars, years and additional months for the term, annual interest rate as a percent, a compound choice from annually through continuously, and, for amortized loans, a payback frequency from daily through yearly. The engine supports 365 daily periods, 52 weekly periods, 26 biweekly periods, 24 half-month periods, 12 monthly periods, 4 quarterly periods, 2 half-year periods, and 1 yearly period.
Worked example
For a $100,000 amortized loan at 6% compounded and paid monthly for 10 years, r = 0.06 / 12 = 0.005 and n = 10 x 12 = 120. The payment is 100000 x 0.005 x 1.005^120 / (1.005^120 - 1) = about $1,110.21; 120 payments total about $133,225, so interest is about $33,225.
How to interpret the result
A payment is a schedule estimate under the chosen compounding and payment conventions, not a lender quote. A shorter term normally raises each payment while reducing the number of interest-bearing periods. Review the schedule because the early rows contain more interest and the later rows contain more principal.
Common mistakes to avoid
Do not enter an annual rate as the periodic rate. Do not use years alone when the remaining term includes months. Keep the compound and payback selections distinct: compounding controls how the rate is converted, while payback controls how often the balance is paid down.
Assumptions and limitations
The calculation assumes a regular fully amortizing balance and does not add origination fees, insurance, taxes, late charges, or prepayment rules. The deferred and bond views share the engine's loan schedule, so they should not be used as a full zero-coupon bond valuation or a contract disclosure.