Money Market Account Calculator — MMA Interest & Growth
See how your money market account grows over time. Enter your opening balance, the current APY, optional monthly deposits, and a time horizon — then get the final balance, total interest earned, and a month-by-month growth curve.
$
%
$
years
Interest compounding
Initial balance plus all contributions plus compounded interest
- 1
Monthly effective rate
(1 + 4.5% ÷ 12)^(12 ÷ 12) − 1 = 0.00375Converts the annual rate and compounding frequency to a monthly rate. - 2
Principal growth
10,000 × (1 + 0.00375)^60 = 12,517.96 - 3
Contribution growth
200 × ((1 + 0.00375)^60 − 1) ÷ 0.00375 = 13,429.11 - 4
Final balance
12,517.96 + 13,429.11 = 25,947.07
How does this calculator work?
A money market account compounds your balance at a variable rate (estimate yours from current bank ads). Balance = P × (1 + r/n)^(n·t) plus a contribution annuity. Enter initial balance, APY, monthly deposits, and time to get the final balance and total interest. Rates are variable — treat the result as a projection, not a guarantee.
Formula
How this is calculated
A money market account (MMA) is a type of deposit account that typically offers a higher interest rate than a standard savings account in exchange for a minimum balance requirement and limits on monthly withdrawals (commonly six per month under traditional Regulation D rules, though many banks have relaxed this since 2020). Interest is FDIC-insured up to $250,000 per depositor per bank.
The balance grows by compound interest: each period the interest earned is added to the principal and itself earns interest in subsequent periods. The formula is P × (1 + r/n)^(n·t) for the opening balance, where r is the annual rate, n is compounding periods per year, and t is the time in years. Many MMAs compound daily or monthly; daily compounding gives slightly more interest than monthly for the same stated APY.
If you make regular monthly deposits, each deposit also earns compound interest from when it is made. The calculator treats these as an ordinary annuity using the monthly effective rate rₘ = (1 + r/n)^(n/12) − 1. Note that MMA interest rates are variable — they track the federal funds rate and can change without notice. The rate you enter is an estimate; actual returns may be higher or lower.
Frequently asked questions
A money market account is an FDIC-insured deposit account that pays a variable interest rate — typically higher than a regular savings account — and may require a minimum balance (often $1,000–$10,000). It is different from a money market mutual fund, which is an investment product and not FDIC-insured.
Unlike a certificate of deposit (CD), an MMA has no fixed term — you can withdraw at any time, subject to monthly transaction limits. The rate is variable and can change with market conditions, whereas a CD locks in a rate for the full term. Regular savings accounts often pay lower rates and have fewer restrictions.
APY (Annual Percentage Yield) already accounts for compounding within the year, while the nominal rate does not. If a bank advertises a 4.5% APY compounded daily, the nominal daily rate is slightly lower (≈ 4.4%) but the effective annual yield is 4.5%. Enter the advertised APY for accurate results.
Also known as
TG we-Calculate Editorial Team. (2026). Money Market Account Calculator — MMA Interest & Growth [Online calculator]. TG we-Calculate. https://we-calculate.com/calculator/money-market-account-calculator
TG we-Calculate Editorial Team. "Money Market Account Calculator — MMA Interest & Growth." TG we-Calculate. 2026. https://we-calculate.com/calculator/money-market-account-calculator.
TG we-Calculate Editorial Team, "Money Market Account Calculator — MMA Interest & Growth," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/calculator/money-market-account-calculator
@misc{wecalculate_money_market_account_calculator, title = {Money Market Account Calculator — MMA Interest & Growth}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/calculator/money-market-account-calculator}}, year = {2026}, note = {TG we-Calculate} }
Did this calculator help you?