Startup runway calculator
Runway is how many months you can keep going before the cash is gone. For a new store it depends on two things: how much you spend each month and how quickly the store starts earning. This calculator runs the numbers month by month, with growth that lasts for a period you choose, and compares the result with a case where growth never comes.
Your cash lasts about 10 months if gross profit grows as planned. With no growth at all, it lasts about 8 months.
- Months of runway
- 10 months
- Cash runs out (month 11)
- Oct 2027
- Costs covered (month 14)
- Jan 2028
With growth
- Starting cash
- $12,000
- Monthly costs
- $1,800
- Gross profit in month one
- $300
- Months of runway
- 10 months
If growth never comes
- Monthly cash burn
- $1,500
- Months of runway
- 8 months
Platform fees are quoted in US dollars. Other currencies use approximate conversion rates, so treat them as estimates.
How this calculator works
Runway matters because cash, not profit, decides whether a new store survives its first months. A store can be improving every month and still run out of money before the improvement pays off. The calculator covers starting cash, monthly costs, gross profit in the first month, monthly growth in that profit and the number of months growth lasts. It shows when cash runs out, when gross profit first covers your costs and a chart of the cash balance. It stops looking after five years.
The steps
- Start with your cash.
- Each month, gross profit equals the first month’s profit grown by your monthly growth rate, for as many months as growth lasts; after that it stays flat.
- Subtract monthly costs and add the result to your cash.
- The month before cash goes below zero is your runway. The no-growth case divides cash by the monthly shortfall.
Assumptions
- Gross profit means sales minus product costs, fees and advertising.
- Growth is the same percentage each month until it stops.
- Costs stay the same. Real costs usually rise as the business grows.
- Owner’s pay counts as a cost only if you enter it.
Two worked examples
Savings and steady growth
Growth carries gross profit above costs in month 16, and the cash never runs out within five years.
With growth
- Starting cash
- $20,000
- Monthly costs
- $1,500
- Gross profit in month one
- $300
- Months of runway
- 60+ months
If growth never comes
- Monthly cash burn
- $1,200
- Months of runway
- 16 months
Growth that never arrives
With no growth, the monthly shortfall is $1,050 and the cash lasts about 7 months. This is the case worth planning against.
With growth
- Starting cash
- $8,000
- Monthly costs
- $1,200
- Gross profit in month one
- $150
- Months of runway
- 7 months
If growth never comes
- Monthly cash burn
- $1,050
- Months of runway
- 7 months
Costs people forget
- Taxes. Profit may be taxed, and some taxes are due in a lump sum.
- Slow payouts. Platforms can hold payouts for days or weeks.
- Stock purchases. Buying stock in bulk uses cash before it earns.
- Personal costs. If the business must also pay for your living costs, include them.
- Annual bills. Domains, software and insurance arrive in lumps.
- A buffer. Plan to stop before cash reaches zero.
- Growth that stalls. Early growth is often fast from a tiny base and slows as it gets harder to find new buyers. That is why the calculator lets growth stop after a set number of months instead of continuing for ever.
Frequently asked questions
What is runway?
The number of months until your cash runs out.
What growth rate should I use?
Use a cautious number. A growth rate of zero shows the worst case.
What is gross profit here?
Sales minus product costs, platform fees and advertising.
Why does the chart stop?
It stops shortly after cash runs out, or after three years if it does not.
Does this include my salary?
Only if you add it to monthly costs.
Is this a forecast?
No. It shows what your assumptions imply, nothing more.
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StartupCostLab provides estimates for planning only. Results depend on the numbers you enter and on fees that platforms change. This is not financial, tax or legal advice. Fee data last reviewed 10 November 2026; confirm current prices on each provider’s own site before you spend money.