A cash reserve. A goal. A clear timeline.

Month-by-month cash plan

Month 0 is today. Each later row is after that month's interest and contributions, before the goal is paid. The goal cost is paid once, at the deadline, and never drawn from the reserve.

How this calculator keeps the reserve and goal separate

1. Choose a reserve target: monthly essential expenses × your chosen reserve months. Current cash fills that target first. Only cash above it starts in the goal pot.
2. Convert APY to a monthly rate: (1 + APY ÷ 100)^1/12 − 1. The same hypothetical rate is held constant; a 4% APY is not modeled as 4% ÷ 12 each month.
3. At each month-end: interest is added on the opening goal balance. Your contribution then tops up an incomplete reserve; any remainder goes to the goal. That new contribution begins earning modeled interest the following month.
4. At the deadline: compare the goal pot with the goal cost. A shortfall is not covered by silently spending the reserve. If the goal is fully funded, show what remains after paying it. Report any remaining reserve gap separately.

A worked example, with no interest

With $15,000 cash, $3,000 essential monthly expenses and a chosen three-month reserve, $9,000 is held separately and $6,000 starts in the goal pot. Twelve end-month contributions of $300 bring the goal pot to $9,600 at 0% APY: $400 short of a $10,000 goal. If current cash were only $8,000, the first $1,000 of contributions would instead fill the reserve gap.

Calculations do not round between months; displayed amounts and CSV monthly rows round to cents. Expenses, contributions and the reserve target stay constant. No reserve interest, withdrawals before the deadline, inflation, taxes, fees, account restrictions, variable rates, debt repayment or other goals are modeled. The investment illustration is simply amount × decline percentage; it is not included in any cash balance.

Zero-dollar goals and zero reserve months are allowed for exploration, not endorsements. All amounts must be nonnegative. Expense inputs are limited to $1 million per month; cash, goal, contribution and independent investment inputs to $100 million each; reserve months to 60; the deadline to 360 whole months.

Savings account or brokerage account? Start with what is actually held.

A brokerage account is an account type, not a promised return. Cash, bank sweep deposits and investment funds can have different risks, access rules and protections. This tool does not select an account, provider or allocation for you.

• Bank deposits: standard FDIC coverage is $250,000 per depositor, per insured bank, per ownership category. Deposits in the same category at the same bank are combined; the number of accounts does not multiply coverage. FDIC coverage explanation.
• Money-market mutual funds: these are investments, not FDIC-insured bank deposits, and can lose value. SEC money-market fund guide.
• Brokerage protection: SIPC concerns missing customer cash and securities when a member brokerage fails; it does not insure market losses. Coverage limits and eligibility apply. What SIPC protects.
• Rate labels matter: a money fund's 7-day yield annualizes a recent income period; it is not the same measure as a deposit APY or a guaranteed future return. Provider yield definitions. Check a provider's effective date, eligibility, fees and product type before comparing offers.

No live rates, affiliate offers or approved provider partnerships are represented here. A balance alone cannot determine an appropriate investment: timing, risk tolerance, liquidity needs, debts and other circumstances matter.

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Methodology reviewed October 25, 2026. Educational scenarios, not personalized financial advice.