Money Market Calculator
Estimate interest on a money market or high-yield savings balance. Enter principal, APY %, and number of days held.
FAQ for this calculator
- APY vs APR?
- APY includes compounding—savings quotes usually show APY.
- Tax on interest?
- Not modeled—interest is generally taxable as ordinary income.
- Variable rates?
- Use today's APY—rates change with Fed policy.
- Money market fund risk?
- Not addressed here—research fund prospectus and SIPC vs FDIC coverage.
How to use the money market calculator
Daily rate from APY compounds over the day count to project balance.
- Enter starting balance.
- Set current APY from your bank or fund.
- Enter days you expect to hold cash.
When to use this calculator
- Parking house down payment for 90 days.
- Comparing two HYSA promotional rates.
- Treasury bill vs MMF yield check.
Examples & walkthrough
- $10,000 at 4.5% APY for 90 days → modest interest vs principal.
- Higher APY or longer days scale interest roughly linearly at low rates.