Every financial article wants to hand you a number: three months, six months, a year of expenses. The numbers are not wrong; they are averages dressed as absolutes. Your number depends on your job, your household, and how long it takes someone in your line of work to find the next position. The honest answer sits between your situation and your comfort.
Build it in stages. The first target is small — one month of essential costs — because one month is achievable and already changes how you respond to bad news. The second target, six months of essential costs, is the one that turns surprises into inconveniences. The last stage is optional and personal.
Keep the fund somewhere separate from your everyday account, so the money is not silently spent, and top it up like a bill: a fixed transfer on payday, whatever the amount. The point of the fund is not the number on a spreadsheet. It is the fact that bad news becomes a footnote rather than a plot twist.