What APY means
APY (annual percentage yield) is the yearly return on a savings balance with compounding already included. That makes the first-year math simple: balance × APY. $10,000 at 0.01% APY earns $1 in a year. At 3.5% APY it earns $350. Same money, very different result, which is the point of the video.
The doubling clock for savings
Doubling time = ln 2 ÷ ln(1 + APY). At 0.01%, that's about 6,932 years. At the national average savings rate reported by the FDIC (0.37% as of Sep 21, 2026), it's about 188 years. At 6%, about 11.9. The Rule of 72 gives nearly the same numbers.
Why rates differ so much
Savings rates vary widely between accounts and change often. Some accounts pay promotional rates for a limited time, cap the balance that earns the top rate, or require things like direct deposit or a minimum balance. Some charge monthly fees or memberships. Before comparing two rates, check those conditions and subtract any fees. The fee field on this page does that: 3.6% on $10,000 with a $50 yearly fee nets $310, not $360.
Insurance: check the bank behind it
FDIC insurance covers deposits up to $250,000 per depositor, per insured bank, per ownership category. Some apps and fintech companies aren't banks themselves; they partner with one. The insurance applies to the insured bank holding the money, so it's worth finding which bank that is. The FDIC's BankFind tool lets you look up whether an institution is insured.
Savings vs inflation
A savings rate below inflation loses buying power over time, even though the balance grows. That doesn't make savings pointless; it's usually meant for safety and quick access, not growth. The inflation page shows the running-in-place math.
What this page doesn't do
It doesn't name or compare any bank, app or account. Type in the rates you're looking at, and the math is the same for all of them. Rates here are what you enter; they aren't offers.
Sources
Last reviewed: Sep 28, 2026