Emergency fund calculator UK: how much should you save?

The simple version

An emergency fund is money set aside to cover essential costs if your income stops or a large unexpected bill arrives. Its job is not to grow your wealth; its job is to buy you time and calm when something goes wrong.

The core calculation is simple. Work out your essential monthly costs, decide how many months of cover you want, and multiply the two together. If your essentials are £2,000 a month and you want four months of protection, your target is £8,000. That figure is your emergency fund goal.

A related idea is your runway, which is how many months your current savings would actually last. Runway is your available cash divided by your essential monthly spending. The target tells you where to aim; the runway tells you where you stand today.

Step one: find your essential monthly costs

The quality of the whole calculation depends on getting this number right, and the key is to use essential spending rather than your normal lifestyle budget. Essentials are the payments that must continue even with no income coming in.

For most UK households that means rent or mortgage, council tax, gas, electricity and water, food, home and other necessary insurance, transport, childcare, and the minimum payments on any debts. It does not mean holidays, streaming subscriptions you could pause, meals out, gym memberships or upgrades. A helpful test is to ask whether missing a given payment would cause genuine harm or merely a little inconvenience. Only the first kind counts.

It is worth building two versions. The first is a bare survival budget of true essentials. The second is a reduced-but-realistic lifestyle that trims the extras without cutting to the bone. The gap between them is often where your most useful decisions live, because it shows how much flexibility you really have if income falls.

Step two: choose your months of cover

How many months you should hold depends mainly on how secure and replaceable your income is. The common guideline is three to six months of essential costs, but that range hides important differences.

Three months is reasonable if you have stable, secure employment, few dependants, and skills that are easy to re-employ. Six months or more makes sense if you are self-employed, work on short or rolling contracts, are the single earner in your household, or hold a specialised role that could take a long time to replace. People with variable income or several dependants often aim higher still. The right figure is personal, and it is better to be honest about your risks than to copy a generic rule.

Step three: multiply to get your target

With those two numbers in hand, the target is straightforward. Multiply your essential monthly costs by your chosen months of cover.

Using the earlier example, £2,000 of essentials and a four-month target gives £8,000. Someone self-employed with £2,500 of essentials aiming for six months would target £15,000. The arithmetic is easy; the value is that it converts a vague worry about not saving enough into a specific, reachable goal you can plan towards.

Step four: measure your runway

Now compare the target with reality. Divide the cash you could actually access in an emergency by your essential monthly spending, and you have your current runway in months. If you hold £4,000 and your essentials are £2,000, your runway is two months.

Seeing that number is often the moment the idea becomes real. A two-month runway against a four-month target tells you exactly how much further you have to go and roughly how long it will take at your current saving rate. It also removes panic, because you now have a plan rather than a fear.

Where to keep it and how to build it

An emergency fund should be safe and instantly accessible, which points to an easy-access savings account or a cash ISA rather than investments that might fall in value at the worst moment. The priority is certainty and speed, not the highest possible return. Keeping the money in a separate account from your everyday spending helps, because funds you do not routinely see are less likely to be spent by accident.

If you are also carrying expensive debt, build a small starter buffer of around one month first, then focus on clearing high-interest balances, then return to filling the fund to its full target. Automating a standing order on payday is the most reliable way to make steady progress without relying on willpower each month.

Couples and households sharing costs need a slightly different approach. If two incomes both cover the essential bills, losing one is less catastrophic than losing the only income in a single-earner home, so a two-income couple might sit at the lower end of the range while a single earner aims higher. It is worth agreeing whose income the fund is really protecting, and whether you hold one shared pot or separate buffers. Finally, remember that an emergency fund is not permanent once built. If you draw on it for a genuine emergency, treat rebuilding it as the next priority, because its whole value lies in being there the next time something goes wrong.

How RedundancyView fits

The website can teach the runway idea, but the personal modelling is where it becomes useful. RedundancyView is built to hold your household costs, savings and income assumptions, calculate your target and runway, and test scenarios such as redundancy, illness or a career break so you can see how long your money would really last. It runs privately on your own device, so you can plan honestly for a difficult situation without sharing your finances with a third-party server.