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Calculators & Tools

An ARM Mortgage Calculator computes monthly payments for Adjustable-Rate Mortgages, which begin with a fixed interest rate period before adjusting periodically based on an index plus a margin. The core formula is P = L * (c * (1 + c)^n) / ((1 + c)^n - 1), where payments are recalculated each time the rate adjusts. Rate caps limit how much the interest rate can change per adjustment and over the life of the loan.