This page explains exactly how American Compound Calculator works — what formulas we use, where data comes from, how often we update, and where our numbers may differ from other sources.
American Compound Calculator uses the standard compound interest formula: A = P × (1 + r/n)^(n×t), where P is the principal amount, r is the annual interest rate, n is the number of times interest is compounded per year, and t is the time in years.
For accounts with regular contributions, we use the future value of a series formula: FV = PMT × [(1 + r/n)^(n×t) - 1] / (r/n), added to the compounded principal.
Our interest rate presets are based on historical and current benchmark rates from the Federal Reserve (FRED), FDIC national rate data, and published financial research. See: Federal Reserve Economic Data (FRED).
All calculations are performed locally in your browser. No input data is transmitted to our servers.
Interest rate presets are reviewed quarterly based on Federal Reserve data and FDIC published averages. The underlying formulas are standard mathematical constants that do not change. When rate presets are updated, we note the update date on this page.
Our results may differ slightly from bank or investment account statements because: (1) we use idealized compound frequency, (2) actual accounts may have fee deductions, (3) contribution timing conventions vary by institution.
Contact us if you notice a discrepancy — see Contact.