How much should an emergency fund be?

Three to six months of essential outgoings (rent or mortgage, bills, food, transport, debt payments, childcare) held in easy-access cash. Nearer six if you are self-employed, on a single income or in a job that would be slow to replace; three can be enough with a stable job and a partner's income. On £2,000 of essentials a month that is £6,000 to £12,000.

Should I build an emergency fund before paying off debt?

A small buffer first, a month or so, then expensive debt, then the full fund. A 22% credit card beats any savings rate, but with no buffer at all the next surprise goes straight onto the card. The debt payoff calculator orders the debts; this one sizes the buffer.

Where should I keep an emergency fund?

Somewhere you can reach it within a day and will not be tempted to spend: an easy-access savings account, or a cash ISA if your interest would otherwise be taxed. Not investments, which can be down when you need them, and not a fixed-term account.

Emergency fund calculator: how many months do you hold?

Months of essential outgoings in accessible cash against a target of three to six, the shortfall, and how long a monthly saving takes to close it: the buffer that stands between a shock and debt. Your figures never leave your browser.

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Worked example

Computed when this page was built by the same engine that runs the calculator above, so the figures below and the live tool can never disagree. Change any input above to see your own.

Inputs
Essential outgoings a month	£2,000
Target	6 months
Held now	£4,000
Saving a month	£300 at 4.0%

Results
Months of essentials held	2.0
Target	£12,000
Shortfall	£8,000
Time to reach the target	25 months

The next question

Which debt should I clear first? →Debt payoff calculator

Or answer it with everything else: the full Hundred Summers plan connects your pay, pensions, savings, property, tax and spending year by year, and stress-tests them across 500 simulated market histories.

Read the guides

Redundancy: the tax playbook →
The £30,000 exemption, what PILON really is, why the excess lands in your worst tax year, and the pension move that can save 40–60%: the decisions that must be made before the settlement agreement is signed.
Inheriting money: the order of operations →
A lump sum arrives: inheritance, redundancy, a house sale. The unhurried sequence: debt, buffer, wrappers, the tax on what the money earns next, and the £2,880 trick for a non-earning partner.
Income protection, critical illness or life cover: which risk are you actually insuring? →
Three policies, three different events. The population odds of each before retirement, what each policy pays and when, why long absence is the risk most households are least covered for, and how sick pay and savings set the deferred period.
ISA or pension? Where long-term money should go, and the Lifetime ISA's place →
The same gross pay by two routes (pension with relief and a tax-free quarter, or ISA after tax and NI) compared on your rate now and in retirement, why the pension usually wins on tax and the ISA on access, and where the Lifetime ISA's 25% bonus fits.
Premium Bonds, cash and tax: where the money you might need should sit →
The personal savings allowance and why higher-rate savers cross it at ordinary balances, the after-tax comparison that decides Premium Bonds against a savings account, cash ISAs, and what inflation does to money that sits still.

Why months, not pounds

The fund’s job is time: the months a lost job, a broken boiler or an illness can be absorbed without borrowing or selling investments at the wrong moment. Measuring it in months of essential outgoings, not total spending, gives a target that scales with your life. Three months suits a stable job and a second income in the household; six or more suits the self-employed, a single income, or a specialised job that takes long to replace.

Order of operations

Build a small buffer first, clear expensive debt, then complete the fund, then invest: the debt payoff calculator and savings growth calculator handle the next two steps. The same months matter for protection: the income protection calculator counts your sick pay and savings against a long absence and marks the deferred period they reach, so a fuller emergency fund buys a cheaper policy. In the Hundred Summers app the buffer is the current account and easy-access savings the stress tests draw on first.

Education, not advice. The right number of months is a judgement about your own job, household and health; the calculator does the arithmetic once you have made it. For a personal recommendation speak to an FCA-regulated financial adviser; free impartial guidance is available from MoneyHelper.

Sources

MoneyHelper, Emergency savings: how much is enough?.