Savings Runway Calculator
Calculate how long your savings will last given your monthly expenses.
What this calculator does
This calculator tells you how long your savings would last if income stopped. Enter your current savings, your monthly outgoings, and the return your savings earn, and it returns your runway in months, the monthly withdrawal that implies, and a sustainable withdrawal rate for context.
Measuring runway in months rather than pounds matters because months answer the real question. Fifteen thousand pounds sounds like a solid buffer until you see it is four months at your current spending. Converting a balance into time is what turns a savings figure into something you can act on.
When to use it
Run it before you need it. The obvious moments are a redundancy consultation, a planned career break, going self-employed, or a period of ill health — situations where knowing your deadline changes how you behave in the first week rather than the last.
It is also the right check when deciding how much to keep in cash. If your runway already runs to fourteen months, further savings are probably better invested in a Stocks and Shares ISA than parked at 4 percent. And it shows the leverage in your fixed costs: cutting £400 a month extends a £30,000 buffer by more than three months, which no realistic savings rate could match.
Understanding the inputs
Current savings should include only genuinely accessible money — current accounts, easy-access savings, Cash ISAs, and any investments you could sell quickly. Pensions do not belong here, since you cannot draw on them before 55. Premium Bonds do count, as they can normally be cashed in within a few working days.
Monthly outgoings is the input that decides everything. Use your actual average over the last three to six months rather than a budget, because budgets systematically understate reality. Run it twice — once at current spending, once at a stripped-back survival level. Annual return should reflect an easy-access account or Cash ISA, typically 4 to 5 percent, and matters far less than the other two figures.
How is this calculated?
Months = log(1 − (savings × r / expenses)) / log(1 + r) × -1. Without interest: savings / monthly expenses.
A worked example
Suppose you have £30,000 in an easy-access account paying 4.5 percent and your outgoings run £2,200 a month. Ignoring interest, that is 13.6 months of runway. With interest earned on the falling balance, it stretches to about 14.0 months — an extra eleven days.
Now cut to a survival level of £1,800 by dropping eating out, subscriptions, and discretionary spending. Runway rises to roughly 17.2 months, adding more than three months from exactly the same savings. Worth noting too: with £30,000 in savings you would receive no Universal Credit, since entitlement stops above £16,000 — so this runway really is all you have.
Limitations and assumptions
The model assumes outgoings stay flat and no income arrives at all, which is deliberately pessimistic and also unrealistic. Real redundancies often bring statutory or contractual redundancy pay, notice pay, and sometimes partial income. It ignores inflation, so a long runway is slightly overstated in purchasing power terms.
It cannot account for the emergency that creates the need in the first place — a boiler replacement, a car failing its MOT, or a period of unpaid sick leave arriving in the same window. And it assumes your savings hold their value, which is only reliable in cash. Money in equities may be well down at precisely the point you need to draw on it.
Common Questions
- What does savings runway mean?
- How many months your savings can cover your outgoings before running out. It is the household version of a company's burn rate. Thirty thousand pounds against £2,200 a month of outgoings is roughly fourteen months of runway — the number that tells you how long you could manage without income.
- How much runway should I have?
- Three to six months of essential outgoings is the standard guidance and achievable for most households. Six to twelve is appropriate if your income is irregular, you are self-employed, or you are the sole earner. Beyond twelve months, cash usually costs more in foregone growth than it buys in security.
- Should I use current outgoings or reduced ones?
- Both, in two runs. Current spending gives the honest baseline. A stripped-back version — removing eating out, subscriptions, holidays, and discretionary shopping — gives your genuine survival runway, typically 20 to 30 percent longer. That second figure is the one that matters in an actual crisis.
- Does the interest rate meaningfully extend runway?
- Barely, over short periods. On £30,000 against £2,200 a month, moving from 0 to 4.5 percent extends runway from about 13.6 months to 14.0 — roughly eleven days. Interest matters across years, not months. Choose an emergency account on access and safety first, rate second.
- Where should emergency savings sit?
- An easy-access savings account or Cash ISA with same-day or next-day withdrawal, at an FSCS-protected provider. Not in equities, which can be down 30 percent exactly when you lose your job, and not in a fixed-rate bond with a 90-day interest penalty. FSCS covers £85,000 per person per banking licence.
- Should I count my pension as runway?
- No. You generally cannot access a pension before 55, rising to 57 in 2028, and doing so before then is only possible in narrow circumstances such as serious ill health. Anything offering early access to a pension outside those rules is almost always a scam that will cost you a 55 percent unauthorised payment charge.
- What about credit cards or an overdraft?
- They extend your options, not your runway. Credit at 25 percent APR converts a cash problem into a debt problem, and arranged overdrafts now typically carry rates around 40 percent EAR. Treat available credit as a last resort sitting behind cash, not as part of the number.
- Do state benefits count?
- They should, but conservatively. Universal Credit typically involves a five-week wait for the first payment and is means-tested against savings — entitlement tapers above £6,000 and stops entirely above £16,000. If you have meaningful savings you may receive nothing, which is precisely why runway matters.
- How does runway differ from an emergency fund?
- An emergency fund is an amount; runway is a duration. The same £15,000 is eight months of runway on £1,900 of outgoings and four months on £3,750. Runway is the more useful framing because it adjusts automatically as your cost of living changes, which a fixed target never does.
Related calculators
- Emergency Fund CalculatorWork out how much you need in an emergency fund based on your essential monthly outgoings.
- Annual Budget TrackerTrack income, bills, expenses, debt payments and savings across all 12 months, with a running balance, spending breakdown and trend chart.
- Savings Goal CalculatorFind out how much to save monthly to reach your savings goal.