Sources and Methodology

We are an independent, informational resource, not a bank or financial advisor. Our calculators use standard, published financial formulas, and our written content is researched from primary government sources. When we state a fact such as an insurance limit or a tax rule, it comes from the official source listed below, not from third party estimates.

Compound interest (maturity value). Our calculators use the standard compound interest formula, A = P x (1 + r / n) raised to the power of (n x t), where A is the final balance, P is the principal, r is the annual interest rate as a decimal, n is the number of compounding periods per year, and t is the term in years.

Interest earned. Interest earned is the final balance minus the principal, Interest = A - P.

Annual percentage yield (APY). We calculate APY using the formula defined under the federal Truth in Savings Act (Regulation DD), APY = (1 + r / n) raised to the power of n, minus 1.

Simple interest. For simple interest, where interest applies only to the principal, Interest = P x r x t.

Early withdrawal penalty. We estimate the penalty as a set number of months of interest on the balance, based on the penalty period you enter. Actual penalty methods vary by bank and are set in your deposit agreement.

Our results are estimates. Actual bank figures may differ due to day count conventions, rounding, and specific account terms.

We rely on the following primary sources for the facts on this Site.

Each calculator takes the figures you enter, applies the relevant formula above, and displays your results. We use APY where a bank quotes APY, and we convert a base rate to APY using the compounding frequency you select. Any rate shown in an example is illustrative and clearly labeled, not a current market rate or an offer.

We review our formulas, figures, and source links on a regular schedule and update them when rules change, such as a change to insurance limits or tax reporting thresholds. Illustrative examples use round, clearly labeled figures so they stay accurate over time regardless of rate movements.

Accuracy matters to us. If you find a mistake or a broken link, please tell us through our Contact Us page and we will review and correct it promptly.