How to use the financial runway calculator
- Enter the savings you can spend, meaning cash and accounts you would actually draw on, and your monthly spending in the first year.
- Enter any monthly income you expect during this time, such as part-time work or benefits. Leave it at 0 if there is none.
- Open More options to set the yearly return on your savings and the yearly rise in spending. Set both to 0 for the plainest version.
- Read how long the money lasts, the balance at the end of each year, and the table that shows how the answer changes if spending were higher or lower.
Formula
Simple runway (months) = savings / (spending - income)
Each month: new balance = balance x (1 + return / 12) + income - spending
Spending in year y = first-year spending x (1 + rise)^(y - 1)
Runway = the number of full months before the balance would go below 0
The simple formula ignores growth and rising costs. The month-by-month version includes them, and stops at 100 years (1,200 months), which the page reports as "more than 100 years".
Worked example
With $30,000 in savings and $3,200 of spending a month, no income, a 3% return and spending that rises 3% a year, the money covers 9 full months. Spending of $28,800 is paid, and the balance earns $392.10 along the way.
The simple formula gives 30,000 / 3,200 = 9.4 months, close to the modeled answer because the runway is short. With $1,000 of monthly income, the same savings last 13 months, and total spending covered is $41,696.00.
The sensitivity table shows that spending 20% lower ($2,560 a month) stretches the runway to 11 months, and spending 20% higher ($3,840) shortens it to 7.
What counts as savings you can spend
Count money you could reach within days without large penalties: checking, savings, money market accounts and maybe taxable investments you would sell. Retirement accounts usually carry taxes and early withdrawal penalties, so many people leave them out of a runway estimate or include only what would remain after those costs.
Be honest about spending, too. Use what you would actually spend during a lean period, not your current budget with every extra included. The budget planner can help you total essential lines, and the emergency fund calculator turns that figure into a target number of months.
Growth and rising costs
Growth helps a little when a runway is short and a lot when it is long. Rising costs push the other way. Because both are assumptions, the defaults are example values, and setting them to zero shows the baseline. If the answer changes a great deal between the two, the plan depends on assumptions and deserves a closer look.
The result is rounded down to whole months. A runway of 9 months means month 10 cannot be fully paid, not that the money vanishes at the start of month 10.
Planning uses
People use a runway number to decide how long they can take between jobs, whether they can afford a career change, how long a sabbatical would last or how much cushion a new business needs. Treat it as a planning range. Add health insurance, one-time costs and tax effects that your own situation calls for, and review the number whenever your savings or spending change.
Assumptions and limits
- Interest is added at the start of each month on the balance, then income arrives and the month's spending is paid.
- Spending is constant within a year and steps up once a year by the rise you enter. Income is held constant.
- The return and the rise in spending are example assumptions, not forecasts. Returns can be negative in practice.
- Taxes on interest or withdrawals, early withdrawal penalties, health insurance changes and one-time costs are not modeled.
- The runway counts full months the money can pay for. The check stops at 1,200 months.
- This is a planning estimate, not financial advice.
Frequently asked questions
How do I calculate how long my savings will last?
Divide your savings by what you spend beyond any income each month. With $30,000 and $3,200 of spending that is about 9.4 months. This page refines that by adding growth, income and rising costs month by month.
What is financial runway?
It is the length of time you can cover your costs from savings before running out, usually counted in months. People use it to judge how long they can go without income or how much cushion a change of plans requires.
Should I include investments in my runway?
Include only what you would really sell and spend, and consider the taxes and market risk on selling. Money you want to keep invested for decades is usually kept out of a short-term runway figure.
Why does inflation matter for a runway?
Costs usually rise over time, so the same lifestyle needs more dollars each year. On a runway of a few months it hardly matters, but over several years it can take months off the answer.
What does "more than 100 years" mean?
It means income and growth cover your spending for the whole 1,200 months checked, so the balance never reaches zero. It is a sign that your plan is sustainable under these assumptions, not a promise.