How to Calculate Burn Rate: Formula, Math, and Common Mistakes

Calculating burn rate is mostly arithmetic, but the way you frame it changes everything. Most founders use the wrong inputs and get a number that flatters them — until reality catches up. This walkthrough shows the actual formulas, the worked examples, and the three traps that produce misleading numbers.

You can run any of these calculations by hand, in a spreadsheet, or with free burn rate calculator. The math is the same. The advantage of the calculator is that it does the runway and zero-date math at the same time.

The Two Formulas You Actually Need

There are two burn rate formulas. Both are simple. They answer slightly different questions.

Gross burn rate = Total monthly operating expenses

Net burn rate = Total monthly operating expenses - Total monthly revenue

That is it. No fancier math. Gross burn tells you what your company would spend with zero revenue. Net burn tells you how fast your bank balance is actually shrinking.

Investors usually want to see both. Gross burn reveals operational discipline (the lower the better at a given stage). Net burn reveals trajectory (negative means you are gaining cash; positive means you are losing it).

Worked Example: SaaS Startup

Let us work through a real example. A 5-person SaaS company has the following monthly costs in March:

Category	Amount
Salaries (5 people)	$48,000
Cloud hosting & infrastructure	$3,200
SaaS subscriptions (Slack, Notion, etc.)	$1,400
Marketing & paid ads	$5,500
Office/coworking	$2,000
Legal, accounting, contractors	$2,400
Total expenses (gross burn)	$62,500

The company also collected $14,000 in subscription revenue that month. Net burn is $62,500 - $14,000 = $48,500.

If the bank balance at the start of the month was $480,000, the runway is $480,000 / $48,500 ≈ 9.9 months. The "zero date" — when the account hits $0 if nothing changes — is roughly 9 months and 27 days from now.

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Worked Example: Reading From Your P&L

If you already have a profit and loss statement, calculating burn rate is even easier. Find the line that says "Total Operating Expenses" — that is your gross burn for the period. Find "Total Revenue" or "Net Revenue" and subtract.

Watch for two gotchas. First, P&L statements often span a quarter or a year. If your P&L is quarterly, divide by 3 to get monthly burn. If annual, divide by 12. Second, accrual accounting may show expenses you have not actually paid yet (and revenue you have not collected). For burn rate, you want cash basis — what actually moved in and out of the bank — not accrual.

If your accounting tool gives you accrual numbers and you cannot easily switch to cash basis, just compare your bank balance at the start of the month to your bank balance at the end. The difference is your real burn rate, with no math required.

The 3 Mistakes That Make Your Burn Rate Look Better Than It Is

Mistake 1: Forgetting one-time expenses. Your "normal" monthly burn might be $50,000, but once a year you pay $25,000 in legal fees, $12,000 in insurance, and $8,000 in tax filings. Annualized, those add roughly $3,750 a month to your real burn. If you only count the recurring costs, your runway projection will be too optimistic by months.

Mistake 2: Counting non-recurring revenue as recurring. A one-time $30,000 consulting deal is not $30,000 in monthly revenue. Founders sometimes average it across the year ("$2,500 a month from consulting") and reduce their net burn accordingly. This works only if you actually expect to repeat the deal next year. Otherwise, your real net burn is higher than your model says.

Mistake 3: Looking at one good month. Burn rate fluctuates. Some months you pay annual insurance, some you make a big hire, some you collect a big invoice. A single month is a snapshot, not a trend. Always look at a 3-month or 6-month rolling average for the truest picture.

How to Calculate It Right Now

Open free burn rate calculator. Enter:

1. Your current cash balance (bank account + any other liquid reserves)
2. Your total monthly expenses (gross burn)
3. Your monthly recurring revenue

The calculator returns gross burn, net burn, runway in months, and the exact date your cash hits zero. It also shows a visual chart of your cash balance over time, which is useful for spotting how a one-month change in spending shifts the timeline.

Do this once a month, the same day every month. Most founders who get blindsided by running out of cash were not bad at math — they just stopped checking.

Frequently Asked Questions

Should I use gross burn or net burn for runway?

Use net burn. Net burn subtracts your revenue and tells you how fast cash is actually leaving your bank account, which is what determines runway. Gross burn is useful for understanding fixed costs, but it overestimates how quickly you will run out.

Do I include payroll taxes and benefits in burn rate?

Yes. Burn rate is total cash out, so include the fully-loaded cost of every employee — gross salary plus payroll taxes plus benefits plus equipment plus any other employer cost. The rule of thumb is that fully-loaded cost is 1.25x to 1.4x base salary.

Should I include depreciation or amortization?

No. Burn rate is cash-based. Depreciation and amortization are accounting adjustments that reduce reported profit but do not represent actual cash leaving your bank account this month. Strip them out.