Articles
The calculators on this site handle the math. These articles go into the questions that come up around that math: how a bank's advertised rate compares to what you actually earn, what the IRS does to your interest each year, whether the popular rules of thumb hold up when you actually run the numbers, and where a few of the internet's favorite compound interest claims came from.
Every article on this site is written by Cedrick Reese and checked before it ships. Any figure computed on the page (a table, a live tool, a worked example) is generated by that page's own code at render, not typed in by hand, and any claim about a law, regulation, or historical record is checked against a primary or well-documented source, linked at the bottom of the article. Nothing here is financial or tax advice.
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APY vs Interest Rate: What Actually Pays You
The stated rate and the number that actually shows up on your statement aren't the same thing. Here's the formula that connects them, plus a live converter.
Taxes on Savings Interest: What Compounding Looks Like After the IRS
Savings interest is taxed as ordinary income the year it's credited, whether you touch it or not. See what that actually does to a compounding balance, before and after.
The 8-4-3 Rule of Compound Interest, Checked With Real Math
The rule says your money grows by the same amount in years 9 through 12 and 13 through 15 as it did in the first 8 years. It's close, not exact, and here's the real breakdown.
What Saving $500 a Month Actually Becomes
Pick a monthly amount and see it grow across every rate and time horizon at once, in a live grid instead of one number for one scenario.
Did Einstein Really Call Compound Interest the Eighth Wonder of the World?
Probably not. Here's where the quote actually traces back to, and why the math behind it is worth knowing regardless of who said it.