See compounding work in real time.
Initial deposit, monthly contribution, APY and time horizon — see your balance grow with monthly compounding.
Why compounding is the most boring superpower in finance
The first year of a savings habit looks unimpressive — $500/mo at 4.5% APY for one year is about $6,150. But run that for 30 years: $389,000, of which $189,000 is interest. The shape of the curve becomes vertical past year 15. Move the time slider to see it.
APY vs. APR — the same number, different direction
APY (Annual Percentage Yield) is the interest you earn on a deposit, expressed as effective annual rate after compounding. APR (Annual Percentage Rate) is the interest you pay on a loan. A 4.5% APY actually delivers slightly more than 4.5% per year because of monthly compounding within the year.
Where to actually put the money
The calculator is rate-agnostic. Common destinations: high-yield savings accounts (currently 4.0-5.0% APY), money market accounts (similar), CDs (usually a touch higher in exchange for locking up the funds), or Treasury bills via TreasuryDirect.gov.
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Monthly payment + total interest.
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P&I plus optional taxes and insurance.
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Time and total interest by monthly payment.
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Yield from a certificate of deposit.