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 expenses, and the return your savings earn, and it returns your runway in months, the monthly withdrawal that implies, and a safe withdrawal rate for context.
The reason to measure runway in months rather than dollars is that months answer the actual question. Twenty thousand dollars sounds like a reasonable buffer until you realize it is four months at your current spending. Converting a balance into time is what turns a savings figure into a decision you can act on.
When to use it
Run it before you need it. The obvious moments are a possible layoff, a planned career break, starting a business, or moving to freelance income — all 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 cash to hold. If your runway is already fourteen months, additional savings are probably better invested than parked. And it is the fastest way to see the leverage in your fixed costs: cutting $700 a month from expenses extends a $45,000 buffer by more than three months, which no realistic interest rate could achieve.
Understanding the inputs
Current savings should include only genuinely accessible money — checking, savings, money market accounts, and taxable brokerage cash. Retirement accounts do not belong here, since early withdrawal costs income tax plus a 10 percent penalty and would give you far less than the face amount.
Monthly expenses is the input that decides everything. Use your actual average over the last three to six months rather than a budget, since budgets systematically understate reality. It is worth running the figure twice — once at current spending, once at a stripped-back survival level with discretionary items removed. Annual return should reflect a high-yield savings account, typically 4 to 5 percent, and matters far less than the other two inputs.
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 $45,000 in a high-yield savings account paying 4 percent, and your expenses run $3,500 a month. Ignoring interest, that is 12.9 months of runway. With interest on the declining balance, it stretches to about 13.2 months — an extra nine days.
Now cut expenses to a survival level of $2,800 by dropping dining out, subscriptions, and discretionary spending. Runway jumps to roughly 16.5 months, adding more than three months from the same savings. That contrast is the practical lesson: in a cash crunch, the expenses line is a lever you control immediately, while the return on savings is close to irrelevant.
Limitations and assumptions
The model assumes expenses stay flat and no income arrives, which is deliberately pessimistic and also unrealistic. Real job losses usually bring some unemployment benefit, severance, or partial income, and real spending changes under pressure. It ignores inflation, so a long runway is slightly overstated in purchasing power.
It also cannot account for the emergencies that create the need in the first place — a medical deductible, an urgent home repair, or a car replacement landing during the same period. And it assumes your savings hold their value, which is only reliable in cash. Money held in stocks may be down sharply at exactly the moment you need to draw on it.
Common Questions
- What does savings runway mean?
- How many months your savings can cover your expenses before running out. It is the personal finance version of a startup's burn rate. Forty-five thousand dollars against $3,500 a month of expenses is about thirteen months of runway — the number that tells you how long you can go without income.
- How much runway should I have?
- Three to six months is the standard emergency fund guidance, which most people can build. Six to twelve is appropriate if your income is variable, you work in a cyclical industry, or you are the sole earner. Anything beyond twelve months in cash usually costs more in foregone returns than it buys in security.
- Should I use current expenses or reduced ones?
- Both, in two runs. Your current spending shows the honest baseline. A cut-back version — stripping out dining out, subscriptions, travel, and discretionary shopping — shows your real survival runway, which for most households is 20 to 30 percent longer. That second number is the one that matters in an actual crisis.
- Does the interest rate meaningfully extend runway?
- Barely, over short periods. On $45,000 at $3,500 a month, moving from 0 to 4 percent extends runway from about 12.9 months to 13.2 — roughly ten days. Interest matters over years, not months. Choose your emergency account for access and safety first, yield second.
- Where should emergency savings actually sit?
- A high-yield savings account or money market account at an FDIC-insured bank, accessible within a day or two. Not in stocks, which can be down 30 percent exactly when you lose your job, and not locked in a long CD. Coverage runs to $250,000 per depositor per bank per ownership category.
- Should I count my 401(k) as runway?
- No. Withdrawing before 59 and a half triggers income tax plus a 10 percent early withdrawal penalty, so you might net 65 cents on the dollar. A 401(k) loan is less punitive but usually becomes due in full shortly after you leave the job — precisely when you needed the money.
- What about credit cards or a HELOC as backup?
- They extend your options, not your runway. Credit at 22 percent APR converts a cash problem into a debt problem, and a HELOC can be frozen by the lender exactly when housing markets weaken. Treat available credit as a last resort behind cash, not as part of the number.
- Does unemployment insurance count?
- It should, but conservatively. State benefits typically replace 40 to 50 percent of prior wages up to a cap, usually for 26 weeks, and there is often a waiting week before the first payment. If you expect benefits, model your expenses net of them rather than adding to savings — that is the more accurate adjustment.
- How does runway differ from an emergency fund?
- An emergency fund is an amount; runway is a duration. The same $20,000 is eight months of runway on $2,500 of expenses and four months on $5,000. Runway is the more useful framing because it automatically adjusts when your cost of living changes, which an amount target never does.
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