Burn Rate Calculator
Gross burn, net burn and how many months of cash are left — modelled with revenue actually growing rather than frozen, because the flat division every other tool does is wrong by months.
Free · No signup · Runs entirely in your browser
Runway is cash divided by net burn — but only if revenue never changes. This burn rate calculator runs both: the flat division every other tool gives you, and the same company with revenue actually growing.
What you have today.
Everything out, per month. This is gross burn.
Cash in, per month. Zero is fine pre-revenue.
Month on month. Set to 0 for the flat answer.
Growing revenue 5% a month buys 4.3 months over the flat answer of 12.5 months.
Spend is held flat across the whole projection. Most companies hire as revenue grows, so read the growth curve as the optimistic bound rather than a forecast.
Runway is bought with shipped work, not saved with spreadsheets. If you are building the product largely on your own, Tekk turns what you want into specs your coding agent can actually execute.
The formulas
gross burn = total monthly cash out
net burn = monthly cash out − monthly cash in
runway = cash ÷ net burn
Three lines, and the last one carries an assumption it never states: that revenue stays exactly where it is for the whole period.
Worked example
$500,000 in the bank, $60,000 of monthly spend, $20,000 of monthly revenue.
| Measure | Working | Result |
|---|---|---|
| Gross burn | monthly spend | $60,000 |
| Net burn | $60,000 − $20,000 | $40,000 |
| Runway, flat revenue | $500,000 ÷ $40,000 | 12.5 months |
| Runway, revenue growing 5%/mo | projected month by month | 16.8 months |
Over four extra months, from one assumption. Nothing about the business changed between those two rows — only whether the calculation was allowed to know the company was growing.
Where it stops being a runway problem
Push the growth rate up and something more interesting happens:
| Monthly revenue growth | Runway |
|---|---|
| 0% | 12.5 months |
| 5% | 16.8 months |
| 10% | never runs out — revenue covers spend in month 13 |
At 10% the company is default alive: current growth carries it to break-even before the money runs out, so it does not need to raise again to survive. The flat calculation reports 12.5 months for that same company and sends the founder out to fundraise from a position they did not actually occupy.
This is why the growth field matters more than the precision of any other input on the page.
Gross or net?
Both, for different reasons.
Net burn is what runway is calculated from, and it is the figure investors ask for. Gross burn is what a month costs if revenue stopped tomorrow — the number that matters when you are assessing how exposed you are to losing a large customer or a channel.
A company with $60,000 gross and $40,000 net burn looks fine on net. If that revenue is one contract, gross is the real number.
What this model assumes
Spend is flat. Real companies hire as they grow. Modelling that would need assumptions about hiring plans that belong to you, not to a calculator, so the growth curve here is the optimistic bound. The honest reading is the range between the two lines.
Growth is constant. Compounding a single rate for three years is not a forecast. It is a way of asking what happens if the last few months continue — useful over six to twelve months, decorative after that.
Revenue means cash collected. If you bill annually in advance or wait 60 days on invoices, recognised revenue and cash received are different numbers, and only one of them keeps the lights on.
How it works
- 1
Enter cash, spend and revenue
Cash in the bank today, everything that goes out each month, everything that comes in. Spend on its own is gross burn; spend less revenue is net burn. Both are shown, because they answer different questions and get quoted interchangeably.
- 2
Set your monthly revenue growth
This is the field most tools do not have. Cash divided by net burn assumes revenue never moves again, which is false for any company that is growing. Set it to zero if you want the flat answer; set it honestly and the burn rate calculator projects the real cash curve month by month.
- 3
Read both numbers and the gap
You get the flat runway, the growth-adjusted runway, and the date the account empties. If growth gets revenue past spend before the cash runs out, there is no runway to report at all — the tool says so, because that is the answer that changes what you do next.
Frequently asked questions
- What is burn rate?
- The rate at which a company spends cash. Gross burn is total monthly cash out; net burn is what is left after cash coming in. A company spending $60,000 and earning $20,000 has a $60,000 gross burn and a $40,000 net burn, and which one gets quoted usually depends on which sounds better.
- How do you calculate runway?
- Cash on hand divided by net burn. $500,000 in the bank against a $40,000 net burn is 12.5 months. That standard burn rate formula is where the burn rate calculator above starts, and it is correct only if revenue never changes for the whole period.
- What is the difference between gross and net burn?
- Gross burn ignores revenue entirely — it is what funding a month costs if sales stopped tomorrow. Net burn subtracts revenue and is the number runway is actually calculated from. Investors usually ask for net; the risk-minded read gross, because it is what you would face if the revenue turned out to be less durable than it looked.
- Why does revenue growth change the runway so much?
- Because it compounds against a fixed spend. On $500,000 of cash, $60,000 of spend and $20,000 of revenue, flat maths gives 12.5 months. Growing revenue 5% a month gives 16.8 — over four extra months from an assumption most calculators do not let you express.
- What does default alive mean?
- That current growth gets revenue past spend before the money runs out, so the company does not need to raise again to survive. At 10% monthly growth on the same numbers, revenue covers spend in month 13 and the cash never reaches zero, so the burn rate calculator reports no runway at all. The flat calculation would have reported 12.5 months and sent you out to fundraise.
- What is the burn rate formula?
- Gross burn is total monthly cash expenses. Net burn is monthly expenses minus monthly cash receipts. Runway is cash balance divided by net burn. The whole burn rate formula fits in three lines — the difficulty is being honest about which costs are really monthly and whether revenue is really flat.
- How much runway should a startup have?
- The common guidance is 18 to 24 months after a raise, on the reasoning that a fundraise takes three to six months and you do not want to start one from a position of weakness. Below 12 months, raising tends to become the CEO's main job whether or not that was the plan.
- Does this cash burn rate calculator account for one-off costs?
- Not directly — it models a steady monthly spend. If you have a large one-off coming, the simplest honest approach with a cash burn rate calculator is to subtract it from the cash balance before entering it, which is equivalent to paying it today and slightly conservative.
- Why is spend held flat in the projection?
- Because modelling spend growth too would require assumptions about hiring that no calculator can make for you. It does mean the growth curve is the optimistic bound: most companies increase spend as revenue grows, which pulls the real answer back toward the flat figure. Read the gap between the two lines as a range, not a forecast.
- What if revenue is shrinking?
- Enter a negative growth rate and the projection handles it — the curve falls below the flat line and runway is shorter than the simple division suggests. This is the case where the standard formula is dangerously optimistic rather than merely imprecise.
- Should I use revenue or cash collected?
- Cash collected. Burn is a cash measure, and for a business billing annually in advance or waiting 60 days for invoices, recognised revenue and cash received can differ by a lot. Using the accounting figure here will make the runway look longer than the bank balance will support.
- Do you store the numbers I enter?
- No. The calculation runs entirely in your browser. Nothing is sent to a server, nothing is logged, and there is no account. Disconnect from the internet and it will still work.
- Why is this free, and what is Tekk?
- Tekk is a spec-driven development platform for people building software with AI coding agents. This calculator costs us nothing to run, and the founders counting their runway are often the same people building the product. No signup, no run limit, no upsell inside the tool.
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