Starting formula
Reserve target = Essential monthly spending × Target months
“Three to six months” is a common rule of thumb, not a law. A dual-income household with stable employment may choose one range; a freelancer with concentrated clients may need a longer runway.
Define essential spending
Include housing, basic food, medication, essential transport, insurance, minimum debt obligations, and dependant support. Keep a second “normal lifestyle” scenario for optional spending. This gives you both minimum and comfortable runway.
Adjust for your risk surface
Consider more runway when one client dominates income, hiring cycles are long, insurance deductibles are high, or family care obligations are substantial. A credit card is not a cash reserve: it creates debt and its availability can change.
Where should it sit?
Prioritize accessibility, understandable risk, and separation from everyday spending. Emergency savings need not maximize expected return. Deposit protection, withdrawal conditions, currency risk, and tax treatment vary by country and provider.
Test it in Cash Years
Enter liquid emergency cash, durable recurring income, and essential spending. Then remove part of the income for a stress scenario. Compare the resulting runway with the range you chose and document why.
Primary reference: Consumer Financial Protection Bureau — an essential guide to building an emergency fund. The guide supports goal-setting and cash-flow management; it does not choose an account for you.