Methodology

These are the formulas behind every Calcapr tool. If a tool behaves differently, it says so on its page.

Loan payment (amortization)

Standard fixed-rate amortization: M = P · r(1+r)ⁿ / ((1+r)ⁿ − 1), where P is the principal, r the monthly interest rate (APR ÷ 12), and n the number of monthly payments. Total interest is M × n − P.

Interest accrual

Monthly: balance × (APR ÷ 12). Daily (credit cards, HELOCs): balance × (APR ÷ 365). Tools state which convention they use.

Compound interest / savings

A = P(1 + r/n)^(n·t) for periodic compounding; tools that model monthly contributions use the future-value-of-an-annuity formula and say so.

Debt payoff (avalanche & snowball)

Month-by-month simulation. Each month: accrue interest on every balance at its own rate, apply the minimum payment to each, then apply any extra payment to the target balance — the lowest-balance (snowball) or highest-rate (avalanche) account, cascading to the next when it's cleared.

Early payoff savings

Total interest under the original schedule minus total interest if the balance were paid at the chosen date. Prepayment penalties, where the tool supports them, are included when provided.

Assumptions & limitations

Results are estimates from the inputs you provide. Rates entered are assumed fixed unless the tool models adjustments. Nothing here is financial, tax, or legal advice — see the disclaimer.