The formula
How to calculate emergency fund months
This is the runway question: with no income at all, how long could the household keep paying what it has to pay? The answer is your savings divided by your essential monthly costs.
Use the stripped-back budget, not your usual one. In a genuine emergency the gym membership, the streaming subscriptions and the restaurant spending stop, which is often 20–30% of normal outgoings and buys a meaningful extra month.
What to enter:
- Accessible savings — cash you could reach within a couple of days
- Essential monthly costs
- Adding each month
No submit button: type and the answer moves. Your inputs end up in the link, so the page can be shared already filled in.
Worked example
Work through the defaults on this page:
- Accessible savings: 9,000
- Essential monthly costs: 2,100
- Adding each month: 300
That gives:
- Months of cover: 4.29 months
- Weeks of cover: 18.62 weeks
- Months until six months of cover: 12 months
Reading the result
Under one month is a live risk — that is the point where a single unexpected bill turns into borrowing. Three months covers most redundancy notice periods. Six is the standard target, and beyond twelve the money is usually working harder somewhere else.
Where this goes wrong. Counting a credit card limit or an overdraft as cover. Both can be withdrawn precisely when your circumstances change, and neither is savings — they are debt you have not drawn yet.
Three to six months for a stable salaried income, six to twelve if you are self-employed, a single earner, or working in a sector where finding the next job takes longer.
Include the contractual minimums, because those still fall due if your income stops. Leave out voluntary overpayments — those are the first thing you would pause.
The answer it gives you is months of cover. With 9,000 accessible savings, 2,100 essential monthly costs and 300 adding each month, that comes to 4.29 months. Change any field and the figure moves with it.