Direct answer
A practical emergency-fund target starts with essential monthly outgoings: the costs that would continue during an unexpected bill or loss of income. Multiply those costs by an editable number of months, then add any separate one-off contingency reserve.
Three to six months is a widely used rule of thumb, including in MoneyHelper guidance, but it is not suitable for every household. ToolBullet therefore shows low, base and high scenarios rather than declaring one target correct.
The calculation
Target reserve = essential monthly expenses × target months + one-off contingencyCurrent coverage in months = current emergency savings ÷ essential monthly expensesThe funding gap is the target reserve minus current emergency savings, floored at zero. If a contribution plan is entered, the current balance earns the monthly equivalent of the annual effective rate before each month-end contribution.
Example
| Input | Amount |
|---|---|
| Essential monthly expenses | 2,500 |
| Base target | 6 months |
| One-off contingency | 1,000 |
| Current emergency savings | 4,000 |
The base target is 2,500 × 6 + 1,000 = 16,000. The funding gap is 12,000, and the current savings cover 4,000 ÷ 2,500 = 1.60 months of essential costs.
At zero interest and 500 a month, the 12,000 gap takes 24 monthly contributions. With a positive annual effective savings rate, ToolBullet converts that rate to an equivalent monthly rate rather than dividing by 12.
What belongs in essential expenses?
| Usually essential | Usually a separate planned fund |
|---|---|
| Housing, basic utilities and communications | Holidays and gifts |
| Basic food and essential transport | Known annual subscriptions |
| Insurance, essential health and care costs | Routine home improvements |
| Minimum debt payments | Expected vehicle servicing |
The distinction is whether the expense is unexpected. MoneyHelper describes sinking funds as pots for known future expenses, while an emergency fund is for genuine shocks such as urgent repairs or income disruption.
Choosing low, base and high scenarios
Consider more than employment status. A household with two stable incomes, broad insurance and low fixed costs may choose a smaller base scenario than a single-income household with dependants or specialised care needs. A self-employed person with variable income may choose a larger buffer.
- Low scenario: a first milestone or a household with strong alternative support.
- Base scenario: the working planning target used for the funding timeline.
- High scenario: a stress case for longer income disruption or larger unavoidable costs.
These are labels, not recommendations. The user sets all three month assumptions.
Liquidity and risk
An emergency reserve needs to be accessible. A higher expected return is not automatically better if the money can fall in value, be locked away or take time to withdraw. The calculator accepts an optional savings rate for planning, but it does not recommend an account or model investment risk, tax or deposit-protection rules.