Sources & Methodology

Introduction

This page explains how we gather financial information, build our calculators, check our formulas, and keep everything accurate over time. If you’ve ever wondered where our numbers come from or how we make sure a calculator is right, this is the page that answers that.

Financial Information Sources

When a calculator or article needs outside information, like how CD interest is regulated or how early withdrawal penalties typically work, we go to primary sources first. These include the FDIC, NCUA, IRS, U.S. Treasury, Federal Reserve, and CFPB, along with official bank disclosures when a specific product is relevant.

We prefer primary sources because they’re the ones setting the rule or publishing the data directly. A regulation described on the FDIC’s own site is more reliable than a summary of that regulation written somewhere else.

Secondary sources come into play when a primary source doesn’t cover a topic in enough detail, or when we need a general industry explanation rather than an official rule. In those cases, we cross-check the information against at least one other source before using it. If we can’t verify something, we leave it out rather than guess.

Calculator Methodology

Every calculator on this site is built on standard, accepted financial formulas, the same math used across the banking and finance industry. We don’t use custom or unusual calculation methods. What changes from calculator to calculator is the purpose, and that shapes the specific inputs, assumptions, and outputs.

Our CD Calculator uses compound interest and APY to project how a deposit grows over its term. The CD Maturity Calculator applies the same core math but focuses on the payout at a specific end date. The CD Comparison Calculator runs those same formulas across two or more offers so you can see the difference side by side. The CD Ladder Calculator extends this further, applying maturity and reinvestment logic across multiple CDs with staggered terms. The CD Early Withdrawal Penalty Calculator uses a separate formula based on penalty terms, applied against the interest already earned.

As we add more finance calculators beyond CDs, each one will follow this same approach: an accepted formula for that specific financial calculation, built around clear inputs and outputs.

Assumptions

Every calculator relies on assumptions to produce a result. Common ones include the APY, deposit amount, interest rate, term length, compounding frequency, and, where relevant, withdrawal timing or contribution frequency.

We don’t hide these. Whenever an assumption affects your result, it’s shown on the calculator itself, either as an input you control or a note explaining what we’re assuming on your behalf. You should always be able to see what went into a number, not just the number itself.

Testing & Validation

Before any calculator goes live, we test it. This includes running multiple input values through it, checking edge cases like very short terms or unusually large or small deposits, and working through the math by hand or in a spreadsheet to confirm the tool matches.

We also check rounding behavior, since small rounding differences can throw off a result if handled inconsistently. Once a calculator’s output matches our manual calculations across different scenarios, it’s ready to publish. We don’t rely on outside certification or third-party audits. This testing is our own, and we take it seriously because the numbers matter.

Content Methodology

The articles on this site exist to explain the calculator next to them, not to fill space. Our process starts with a real question someone would ask, like “how does a CD ladder actually work,” then moves into research, verification against our sources, and an explanation of the formula in plain language.

From there, we build worked examples using the same logic as the calculator, so you can follow the math step by step if you want to. Every article is reviewed for clarity before it goes live. If a page doesn’t help you understand the calculation better, it doesn’t serve its purpose.

Updates & Improvements

Our methodology isn’t fixed in place. We update it when financial regulations change, when we find a better or more accurate way to calculate something, when a bug turns up in a formula, or when we can explain a concept more clearly than before. As we expand into new calculators, this page and our process will grow with them.

Transparency

Everything that shapes a result on this site is meant to be visible to you: the assumptions behind a calculator, the formula it uses, a worked example showing the math, and the reasoning in the article next to it. We’d rather show our work than ask you to take a number on faith.

Limitations

Our calculators give you an estimate based on the numbers you enter. Your actual outcome with a real bank or credit union can differ, because of factors like specific institution policies, taxes, fees, exact account terms, and financial conditions that change over time. Use our results as a strong starting point for your own research, not as a final, guaranteed figure.