THE NUMORIX GUIDE
How to use the Emergency Fund Calculator
Last reviewed September 14, 2026
What this calculator does
The target is monthly essential expense assumption times months of expenses.
Formula and method
The target is monthly essential expense assumption times months of expenses. Shortfall is max(0, target - current savings). If a positive contribution exists, the engine simulates each month as balance x (1 + savingsInterest/12) + monthly contribution until target is met or 600 months pass.
Variables and inputs
Enter monthly expenses, target months of expenses, current savings, monthly contribution, and annual savings interest. Expenses, savings, and contribution are dollars; months of expenses and time-to-goal are months; savings interest is an annual percentage.
Worked example
With $3,500 monthly expenses and a six-month target, target fund is 3,500 x 6 = $21,000. If current savings are $5,000, shortfall is $16,000. At 4% annual interest and a $500 monthly contribution, month 1 becomes 5,000 x (1 + 0.04 / 12) + 500 = $5,516.67.
How to interpret the result
The result shows a chosen reserve target, current shortfall, and modeled months to reach it. The target should reflect the stability of income, household obligations, insurance coverage, and access to other liquid resources rather than a universal month count.
Common mistakes to avoid
Use essential expenses rather than discretionary spending if that matches your emergency definition. Do not count invested assets that may be volatile or hard to access as cash without considering the risk. Enter contribution per month, not annual contribution.
Assumptions and limitations
The route assumes stable expenses, contributions, and interest and does not model taxes, fees, withdrawals, unemployment duration, inflation, or changing household needs. It stops after 600 months and treats all current savings as earning the entered rate.