Cash Runway Calculator: a practical guide
How long could my cash last after monthly income and spending?
Estimate how long cash could last when monthly spending is higher than cash coming in.
By VolatileShares · Example version 1 · Updated . Hypothetical inputs, not financial recommendations or live company data.
A worked example, in plain English
The idea in 10 seconds: A phone battery for your cash: how many months before the spendable part runs out?
A cash countdown, with the assumptions exposed.
Net outflow is spending minus income. The reserve is not spendable in this example.
- Estimated runway (months)
- 5
- Cash above reserve
- $5,000.00
- Entered monthly cash burn
- $1,000.00
Walk me through the full calculation
Of $6,000.00 in entered cash, you hold $1,000.00 in reserve, leaving $5,000.00 for the scenario. At $1,000.00 of net cash burn per month, that covers about 5 months, or 5 complete months at that same rate.
Net cash burn means cash going out after cash coming in, not a loss on an income statement. Verify the cash-flow period and available cash, and review debt payments or one-off obligations separately. Changing burn or new financing changes the estimate; this is not a predicted bankruptcy date.
Inputs used for this example
These are the calculator's example defaults, not suggested amounts or rates. Market calculators initially display USD. Change currency in the toolbar without creating a personal profile. Under optional Location & display settings, choose an example country for its currency and available historical CPI. Review any example household size and rent assumption before explicitly applying local assumptions: matching unedited budget/inflation fields change, while edited or restored inputs are kept. Lifestyle budgets are fictional examples, not measured national averages. Local tax, pension and borrowing links are guidance, not personal calculations. Switching currency alone does not change percentages, ages or share counts.
- Cash available now (USD)
- 6,000
- Cash you will keep aside (USD)
- 1,000
- Spending above cash income each month (USD)
- 1,000
Work backwards from your goal
What monthly outflow would leave at least this much runway?
Start with the months you want and solve for monthly net outflow.
Choose Work backwards, enter your target and the few essential inputs, then choose Calculate my goal. The answer is checked with the same forward calculation and applied in one step. Example assumptions are disclosed under More options. Expand Calculation details & tools only if you want more detail. Impossible or out-of-range goals show an error instead of invented numbers. Long numbers display commas while editing; calculations and saved snapshots keep the original precision.
Return to the interactive calculator above →How the calculation works
Usable cash = available cash - reserved cash. Runway in months = usable cash / average monthly net cash burn. No finite depletion estimate is given when burn is zero.
What this cannot tell you
Use verified cash balances and a non-negative average monthly net cash outflow, not accounting losses. Assumes constant burn, no new financing and no one-off obligations. Reserve is your assumption, not a recommended amount. This is not a solvency or bankruptcy forecast.
Changing an assumption changes the example, not the future. Verify source dates and actual product, tax and lending terms before relying on any result. These tools do not replace appropriately qualified advice.
20% less burn can buy 25% more time
With the same usable cash and a positive, constant burn rate, reducing monthly burn to 80% of its original value extends modeled runway by 25%: 1 / 0.8 = 1.25. New financing, obligations or changing burn can invalidate that simple model.
Illustrative arithmetic, not market evidence or a promise of returns.
Keep a useful starting point
In the interactive calculator, compare different assumptions or explicitly save a named snapshot to My browser notebook. Saving is optional and browser-only, not an account or cloud backup. Revisit it on the same browser profile; restoring never refreshes prices or assumptions.