Money Market Account Calculator
Enter your opening deposit, annual rate, compounding frequency, and recurring contributions to project your ending balance, total deposits, interest earned, and APY — with a growth waterfall showing exactly how each component builds your final balance.
Quick preset
Account inputs
Compounding
Recurring contributions (optional)
What to do next
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Step-by-step
What this calculator does
This money market account calculator projects the future value of a deposit account using compound interest plus optional recurring contributions. It separates the two growth sources — the opening deposit growing through compounding, and the recurring contributions accumulating as an annuity — then combines them into an ending balance.
The growth waterfall shows each component clearly: how much of the ending balance came from the principal growing, how much came from contributions growing, and how much was earned purely from interest. APY is also calculated from the nominal rate and compounding frequency so you can compare the effective yield across accounts that compound at different intervals.
Formulas used
P = opening deposit · r = nominal annual rate
m = compounding periods/year · t = years
Effective rate per contribution period =
(1 + r ÷ m)^(m ÷ contrib_freq) − 1
Contributions FV (ordinary annuity, end timing) =
PMT × ((1 + eff_rate)^n − 1) ÷ eff_rate
Contributions FV (annuity due, begin timing) =
above × (1 + eff_rate)
APY = (1 + r ÷ m)^m − 1
Interest earned = Ending balance − Total deposited
How to use
- Select a preset or enter your own opening deposit, annual rate, and time horizon.
- Set the compounding frequency to match what your bank uses — most MMA accounts compound daily or monthly.
- Enter a recurring contribution and its frequency if you plan to add money regularly. Use 0 to model the opening deposit alone.
- Choose contribution timing — beginning of period earns one extra period of interest per contribution vs end of period.
- Click Calculate — the waterfall shows how each component builds the ending balance.
Example calculations
Total deposited: $17,000
Interest earned: $2,688
Ending balance: $19,688 · APY 4.594%
Total deposited: $24,400
Interest earned: $2,312
Ending balance: $26,712 · APY 4.282%
Total deposited: $90,000
Interest earned: $33,903
Ending balance: $123,903 · APY 4.917%
Total deposited: $20,000
Interest earned: $7,464
Ending balance: $27,464 · APY 4.594%
FAQ
What is the money market account growth formula?
The opening deposit grows as FV = P × (1 + r ÷ m)^(m × t), where P is the deposit, r is the nominal annual rate, m is compounding periods per year, and t is years. Recurring contributions are treated as an annuity using an effective rate per contribution period. APY = (1 + r ÷ m)^m − 1 converts the nominal rate to an effective annual yield.
What is the difference between nominal rate and APY?
The nominal rate is the annual rate the bank quotes before compounding effects. APY (Annual Percentage Yield) reflects how much you actually earn in one year after compounding is applied. Daily compounding at 4.5% nominal produces an APY of about 4.603% — slightly higher than the nominal rate. Always compare accounts using APY, not nominal rate, for a fair comparison.
Does contribution timing really matter?
Yes, meaningfully for longer terms. Beginning-of-period deposits earn one extra compounding period compared to end-of-period deposits. Over 10 years of monthly contributions at 4.5%, the difference between beginning and end timing can add several hundred dollars to the ending balance. The impact grows with rate, time horizon, and contribution amount.
Why does daily compounding produce a higher APY than monthly?
Because interest is applied more frequently, and each application earns interest on the previously credited interest. A 4.5% nominal rate compounded daily produces APY of about 4.603%, while monthly compounding produces 4.594%. The difference is small but compounds meaningfully over long periods and large balances.
What if the rate changes during the term?
This calculator assumes a constant rate for the full projection period. Real money market account rates are variable — they can change with the federal funds rate or bank policy at any time. Use this calculator for planning scenarios, not as a guarantee of actual returns. Running multiple scenarios with different rate assumptions is a good way to stress-test your savings plan.
Is this the same as a money market fund?
No. A money market account is an FDIC-insured deposit account at a bank or credit union. A money market fund is a type of mutual fund that invests in short-term securities and is not FDIC insured. This calculator models a money market account (deposit account), not a money market fund. The returns, risks, and access rules are different between the two.
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Disclaimer: This calculator is for educational and planning purposes only. It does not provide financial advice. Real money market account performance may differ due to variable rates, tiered APY structures, minimum balance requirements, fees, taxes, early withdrawal restrictions, and bank-specific terms. FDIC insurance limits apply.