Almost every piece of advice on emergency funds says the same thing: keep three to six months of expenses. Almost none of them say which. That range is a doubling — on two and a half thousand a month it is the difference between seven and a half thousand pounds and fifteen — and being told to pick a number somewhere inside it is not much help when the whole difficulty is knowing where you sit.
This calculator puts you somewhere specific, and shows the reasoning it used. If the answer looks wrong you can argue with an input rather than with a black box.
This is for anyone who has read that they need three to six months of expenses and wants to know which. It assumes you have some capacity to save; if you have none right now, the number it produces is still worth knowing, but the timeline it gives you will not be.
This calculator needs JavaScript. The rule of thumb without it: start at three months of essential costs. Add a month if your work is insecure, two if your income varies, three if you are self-employed. Add one if anyone depends on your income, two if several do, and one more if you are the only earner supporting them. Multiply your essential monthly costs by that, and treat three months above it as the comfortable end.
What moves your number inside the range
Three months is the floor, and it exists because that is roughly how long it takes to find comparable work when nothing has gone badly wrong. Everything above it is an adjustment for how likely a gap is and how expensive it would be.
How your income arrives. A salaried job in a stable sector is the base case. Commission, shifts and bonus-heavy pay mean a bad quarter looks like a small emergency before anything has actually happened. Self-employment means the gap between work ending and money arriving can be months even when the work itself is fine.
Who depends on it. Dependants raise both the cost of a gap and your tolerance for risk during one. Being the only earner supporting them removes the fallback of a second income, which is why the calculator adds for that separately rather than folding it in.
What it deliberately does not ask about is your income. The fund covers essential costs, not earnings, and someone on a high salary spending nearly all of it needs more cover than someone on half as much who spends a third. Scoping those essential costs honestly is the single input that matters most.
A worked example
Someone self-employed, with two dependents and no second earner in the household, whose essential costs are $2,800 a month. They have $4,000 set aside and can save $600 a month.
Self-employment is the largest single factor here, and having dependents with no second income behind them adds to it. Their range comes out at eight to eleven months rather than the usual three to six — $22,400 to $30,800.
The gap to the lower figure is $18,400, which at $600 a month takes 31 months, or two years and seven months. That is a long time, and seeing it is the point. A salaried person with a partner also earning would be told three months and $8,400 on the same expenses — a target they could reach in eight months. The advice that says "three to six" without saying which is hiding a difference of two years.
Where the money should sit
Somewhere you can reach it the same day. That is the whole specification.
The temptation is to chase a return on a sum that size, and it is worth resisting: an emergency fund that is locked in a fixed-term account, or invested in something that might be down twenty per cent in the month you need it, is not an emergency fund. The interest field here defaults to zero for that reason. Enter a rate if your instant-access account pays one, but treat the growth as incidental rather than as the point.
There is an upper limit too. Past about twelve months of costs, cash held for emergencies is losing to inflation with no offsetting benefit, and the surplus is usually better invested — which the compound interest calculator shows the long-run effect of.
Before you build it
One case is worth checking first. If you are carrying debt at a high rate — a credit card at twenty per cent or more — then money sitting in a savings account earning nothing while that interest accrues is costing you every month. The usual advice is to hold one month of costs as a buffer, clear the expensive debt, and then build the full fund. The debt payoff calculator shows what that debt is actually costing you a year.
If the monthly figure looks impossible, the honest answer is that the first month of cover matters far more than the last. Getting from nothing to one month changes what a broken boiler does to you; getting from eight months to nine mostly does not.
Our saving guides cover the habit side, and emergency fund basics goes through the same ground in more depth.