HYSA Calculator
Project how a high-yield savings account balance grows from a starting deposit, monthly contributions and APY -- compounded the way real HYSAs actually credit interest.
The bank's stated annual percentage yield.
Balance
$19,629.26
Total deposited
$17,000.00
Interest earned
$2,629.26
APY is variable on real HYSAs -- it can rise or fall with the Fed funds rate at any time, so this is a snapshot at today's rate, not a locked-in promise for the full 5 years.
How it's calculated
A bank's stated APY already IS the effective annual growth rate -- by definition, it's the actual return a deposit earns in one year including compounding. So this calculator treats it as a single annual period at that rate, then converts it to an exact monthly rate for the month-by-month simulation every tool on this site shares:
monthly rate = (1 + APY)1/12 − 1
Treating the entered APY as a nominal rate and compounding it further (daily or monthly) on top of that would overstate growth beyond what the bank actually credits -- a common mistake this calculator deliberately avoids.
Worked example
The calculator's own defaults: $5,000 starting deposit, $200/mo contribution, a 4.5% APY, over 5 years.
| Total deposited | $17,000.00 |
| Interest earned | $2,629.26 |
| Final balance | $19,629.26 |
Plug the same numbers into the calculator above and it reconciles to the cent -- and as a sanity check, a $10,000 deposit at exactly a 4.5% APY for exactly one year with no contributions grows to precisely $10,450, confirming the APY is applied as the true annual rate, not compounded a second time.
Frequently Asked Questions
What's the difference between APY and interest rate?
APY (annual percentage yield) is the actual amount your deposit earns in one year, already including the effect of compounding -- it's the figure banks are legally required to advertise under the Truth in Savings Act. A "nominal" or "interest" rate, by contrast, doesn't include compounding, so it understates real growth. This calculator treats the APY you enter as the true effective annual rate, then re-bases it to an exact monthly rate -- it doesn't compound an already-compounded number a second time.
Are HYSA funds FDIC insured?
Yes, at an FDIC-member bank: deposits are insured up to $250,000 per depositor, per insured bank, per ownership category -- principal plus any accrued interest, combined across your checking, savings and CD balances at that same bank (source: FDIC.gov). If your balance is likely to exceed that at one bank, spreading it across separate FDIC-insured banks (or ownership categories) keeps the excess covered too.
Why does my APY matter more than I'd expect over several years?
Because interest earns interest -- a 4.5% APY compounded monthly for 5 years grows a deposit by more than 5 x 4.5% simple interest would suggest, and the gap widens every year you leave the money in. The calculator's own worked example below shows the exact effect: check what a 1-2 percentage-point difference in APY does to the same deposit over your own real time horizon.
Will my HYSA's rate stay the same the whole time?
No -- unlike a CD, a high-yield savings account's APY is variable and can change at any time, typically tracking the Federal Reserve's target rate. This calculator projects forward at a single, fixed rate for simplicity; a real HYSA balance's actual growth will differ as the rate moves, which is also true of every other online HYSA calculator using this same simplification.
Figures on this page are estimates from the inputs you enter, not financial advice, and this site is not affiliated with any employer, plan administrator, bank or the IRS. Real accounts vary by plan rules, taxes and fees this tool doesn't model -- see the Terms.