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Business & Tax
Understand gross burn, net burn, and runway. Learn how to manage startup cash consumption.
By FreeCalculators Editorial · Published 2026-09-01 · Updated 2026-09-04 · 4 min read · 944 words
Burn rate is the amount of cash a business consumes each month. Gross burn is total cash out; net burn is cash out minus cash in, and it is the figure that determines survival. Divide cash on hand by net burn and you get runway in months, the single number that dictates whether the next decision is about growth or about cuts. Both figures are cash measures, so accounting profit is irrelevant to them.
Gross burn answers how expensive the business is to run. Net burn answers how long it can keep running. A firm spending $95,000 a month and collecting $60,000 has a gross burn of $95,000 and a net burn of $35,000, and it will read as either alarming or comfortable depending on which number someone quotes at you.
Use cash actually received, not invoiced revenue. This is where accrual accounting misleads founders: a month with $80,000 of signed revenue and $20,000 collected burns cash like a $20,000 month. The Federal Reserve Small Business Credit Survey has repeatedly found that a large share of small firms hold cash buffers measured in weeks rather than months, which is why the collected-cash version of the calculation is the one that matters.
| Measure | Formula | What it tells you | Common error |
|---|---|---|---|
| Gross burn | Total monthly cash outflow | Cost of running the business | Including a one-off equipment purchase |
| Net burn | Cash out minus cash collected | Speed the reserve is draining | Using invoiced revenue, not receipts |
| Runway | Cash on hand / net burn | Months until the account is empty | Assuming burn stays flat as you hire |
| Trailing 3-month net burn | Average of last three net burns | A stable planning figure | Averaging away a rising trend |
Computing burn and runway from a real month (2026)
Cash outflows Payroll and contractors ............ $52,000 Rent and utilities ................. $ 6,800 Software and tooling ............... $ 4,300 Marketing .......................... $18,000 Everything else .................... $ 9,900 Gross burn ......................... $91,000 Cash collected this month ............ $58,000 Net burn = $91,000 - $58,000 ......... $33,000 Cash in the bank ..................... $412,000 Runway = $412,000 / $33,000 .......... 12.5 months If a $9,000/month hire is added: Net burn ........................... $42,000 Runway ............................. 9.8 months
There is no universal target, because burn is only meaningful against runway and against what the spending is buying. The useful test is burn multiple: cash burned divided by net new annual recurring revenue or gross profit added. Spending $33,000 a month to add $30,000 of annual gross profit is a losing trade; spending it to add $120,000 is a reasonable one.
Track burn monthly on collected cash, plot the three-month trend rather than the point value, and recompute runway every time you add a fixed cost. Rising gross burn with flat net burn means revenue is keeping pace and is usually fine. Flat gross burn with rising net burn means collections are slipping, and that is the pattern that ends businesses.
Comprehensive Guide
Read our business and tax guide for margins, payroll, and tax planning.
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How this guide was created
This guide was written and reviewed by FreeCalculators Editorial, drawing on published formulas, official government sources, and real calculator outputs from our 4 calculators in this category. Every claim is sourced; every formula is auditable. Read our review policy.