Cash Runway Calculator
Your cash runway is how long your money lasts at your current rate of spending. Divide the money you can spend by what leaves your account each month, and you get the number of months before you hit zero. If you have 4,200 and spend 1,400 a month, your runway is three months. This calculator does that day by day and gives you the date, including any payments you are still waiting on.
Money you can actually spend, across every account.
Rent, bills, food, subscriptions, everything.
Payments you are expecting (optional)
This is the part generic calculators leave out. An invoice that lands after you run out does not help you.
None added. The projection below assumes nothing comes in.
Working out your runway…
This is a snapshot for today. Guardrail keeps it updated as your balance and bills change, and tracks each bill on its own date instead of an average.
Track this over time, freeNo bank connection. Manual input only.
How to calculate cash runway yourself
- 1
Add up the money you can actually spend
Total the balances across every account you spend from. Leave out money that is already committed, such as tax you are holding back.
- 2
Work out what leaves each month
Add together rent or mortgage, bills, food, transport, subscriptions and loan payments. Use what you actually spend, not what you intend to spend.
- 3
Add the payments you are expecting
Enter each one on the date you realistically expect it to land, not the date you invoiced it. If a client habitually pays late, use the late date.
- 4
Read the date, not the average
The result is the first day your balance is projected to go below zero, along with the lowest point it reaches. That date is the thing to act on.
A worked example
Say you have 3,000 in the bank and spend 2,000 a month. Your daily spend is about 65.75, so on a simple division you have roughly 45 days.
Now add a real detail: a client owes you 2,500 and normally pays around 40 days after invoicing. The average says you are fine. The day-by-day projection says you drop below zero on day 46, six days before the money lands. Those six days are the whole problem, and an average will never show them to you.
That is also why the fix is usually not spending less. Getting that invoice paid a week sooner moves the date more than trimming a subscription does.
What counts as a decent runway
Three to six months of outgoings is the figure most often quoted for people without a salary. It is a reasonable target rather than a rule, and it is worth being honest that it is out of reach for a lot of people who need this calculation most.
If you are under a month, the useful question is not how to reach six months. It is which single payment, moved or chased, buys you the most days. That is a much smaller question and you can usually answer it today.
Why most runway calculators get this wrong
Most of them divide a balance by a monthly figure and stop there. That works if you are paid the same amount on the same day every month. If you are a freelancer, a contractor or on commission, it hides the exact risk you are trying to see, because it treats a payment due on the 25th as though a portion of it arrives every day.
Runway ends on the first day your balance goes below zero. Not at the end of the month, and not on average. A calculator that cannot place a payment on a date cannot tell you that day, which is the only output that changes what you do next.
Common questions
- What is cash runway?
- Cash runway is how long your money lasts at your current rate of spending. Divide the money you can actually spend by what leaves your account each month, and you get the number of months before you hit zero. The term comes from startup finance but it applies to anyone whose income does not arrive on a fixed monthly cycle.
- What is a good cash runway?
- For someone with irregular income, three to six months of typical outgoings is a common reference point. Under one month, a single late invoice can turn into a missed payment. This is a general benchmark rather than advice about your situation, and the right number depends on how reliably you get paid.
- Does this calculator need my bank details?
- No. It runs entirely on figures you type in. There is no account, no signup, no bank connection and no Plaid link. Nothing you enter is sent anywhere, and the numbers stay in the page address so you can bookmark a result.
- How is this different from dividing my balance by my monthly spending?
- Dividing gives you an average and ignores dates. If your rent leaves on the 1st and a client pays on the 20th, the average hides the fact that you are short in between. This calculator projects day by day and lets you place expected payments on the day you actually expect them, so a payment that arrives after you run out does not rescue the result.
- Why does an earlier payment extend my runway so much?
- Because runway ends at the first day your balance goes below zero, not at the end of the month. Money that lands before that day keeps the balance above the line and pushes the date out. Money that lands after it does not help, however large it is. That is why chasing an invoice is often worth more than cutting spending.
Guardrail produces cash-flow projections, not financial advice. The projection is only as good as the figures and dates you enter, and it cannot account for anything you have not entered. Written by George I., who spent twenty years in payments and settlement timing.
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