Calculation methodology

Last updated: 2026-08-14

Vicaya calculators are built as deterministic estimate tools. The result comes from the values entered on the page plus the formula and assumptions printed near the calculator. A changed input should produce a changed result for a clear reason.

Formula approach

Mortgage and loan calculators use standard amortization formulas where the payment is derived from principal, periodic rate, and number of periods. Payoff calculators then walk the balance period by period so extra principal, final payments, and remaining balances are based on a schedule rather than a shortcut.

Paycheck approach

U.S. paycheck pages estimate gross pay, federal withholding, FICA, deductions, and supported state or local rules using the inputs shown on the page. Payroll laws and withholding methods are simplified into calculator assumptions, so the result is an educational estimate, not payroll instruction.

Rounding

Calculations keep more precision internally than the screen shows. Displayed currency is rounded to the relevant minor unit, such as cents for U.S. dollars. A final schedule row may absorb a small difference so the balance reaches zero.

Charts

Donut and balance charts are generated only from real calculation output. A donut needs component parts, such as principal, interest, fees, tax, or insurance. A balance chart needs a schedule or projection, such as an amortization table or year-by-year investment balance.

For examples, use the mortgage amortization calculator, credit card payoff calculator, or investment return calculator.