How Do You Calculate Burn Rate in Excel?

Somebody asks how long the money lasts, and the honest answer is usually a shrug. The bank balance is on screen, last month's expenses are in an export somewhere, and the number that actually matters — how much cash leaves the business in an average month — has never been written down in one place.

Burn rate is that number. It is one of the few metrics you can calculate properly in a spreadsheet in about ten minutes, and one of the few where a spreadsheet is genuinely the right tool rather than a compromise.

The catch is that there are two different burn rates, three common ways to average them, and a popular method that quietly flatters the result. Pick the wrong combination and you will produce a runway figure that is months too optimistic, which is exactly the kind of error nobody notices until it is too late to act on.

This guide covers the formula, how to build it from your own cash balances, how to turn it into runway, which variant to use when, and the specific ways the Excel version goes wrong.

The Short Answer: The Burn Rate Formula in Excel

Net burn rate is the cash you lose in a month. The most reliable way to calculate it in Excel is from your opening and closing cash balances rather than from an expense list:

=(B2-B13)/12

Where B2 is your cash balance twelve months ago, B13 is your cash balance today, and the result is your average monthly net burn. A positive result means you are losing that much cash each month. A negative result means you are cash-flow positive and not burning at all.

For gross burn — total operating cash out, ignoring any revenue coming in — sum the outflows instead:

=SUM(C2:C13)/12

Where column C holds total monthly cash expenses.

Both formulas are averages over twelve months. That window is deliberate, and the next sections explain why a shorter one will mislead you.

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What Burn Rate Actually Measures

Gross burn vs net burn

Gross burn is everything going out: payroll, rent, software, contractors, ad spend, tax. It answers "what does it cost to keep the lights on for a month?"

Net burn subtracts the cash coming in. It answers "how much are we actually losing?" Net burn is the number that drives runway, because revenue genuinely does extend how long you last.

The two can tell opposite stories. A business with £80,000 of monthly costs and £75,000 of monthly revenue has a punishing gross burn and a trivial net burn. Report only the gross figure and you look like you are in trouble. Report only the net figure and you hide how exposed you are if a single large customer leaves.

Calculate both. They cost one extra column.

Why the cash balance method beats adding up expenses

Most people's first instinct is to total the expense column. It feels more precise because it is itemised. It is usually wrong, because an expense list almost never captures everything that moves cash.

Things that typically go missing: tax payments, loan repayments, equipment bought outright, refunds issued, payment processor fees netted off before the money arrives, and anything paid from a second account nobody remembers.

Your bank balance has no such gaps. The difference between two balances is the truth about how much cash left, whether or not anybody categorised it. Start from the balance, then use the expense breakdown to explain the number rather than to produce it.

The one adjustment worth making: if you raised money, got a loan, or took a large one-off payment during the window, strip it out. Otherwise an investment makes your burn rate look like a surplus.

=(B2-B13+D14)/12

Where D14 is total non-operating cash in over the period.

How to Build It in Excel, Step by Step

Set up a plain monthly sheet. Thirteen rows of data gives you twelve months of change.

1. Column A: month-end dates, oldest at the top. Use real dates, not text, so Excel can sort and chart them.
2. Column B: closing cash balance for each month, taken from the bank, not from your accounting software's accruals view.
3. Column C: total cash out that month, if you want gross burn as well.
4. Column D: any non-operating cash in — funding, loans, asset sales.
5. Column E: monthly net burn, as =B2-B3-D3 filled down. Each row is one month's cash movement with funding removed.
6. In a summary block, average it: =AVERAGE(E2:E13) for the twelve-month figure.

Keep the summary block separate from the data rows. Burn rate calculations get copied into decks and board packs, and a summary that sits apart from the raw months survives that copying.

Two formatting details that prevent misreadings. Format the burn cells so a loss reads as positive and label the header explicitly — "Net burn (cash out per month)" rather than just "Burn". And use =AVERAGE() rather than =SUM()/12 wherever a month might be missing, because AVERAGE ignores blank cells while dividing by a hardcoded twelve does not.

If you want a rolling view instead of a single figure, add a column with =AVERAGE(E2:E4) filled down for a three-month rolling average. Charting that column next to the twelve-month average is the fastest way to see whether burn is accelerating.

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How to Turn Burn Rate Into Runway

Burn rate on its own is trivia. Runway is the decision-making number:

=B13/F2

Where B13 is current cash and F2 is average monthly net burn. The result is months of runway at the current rate.

Three rules keep that figure honest.

• Use net burn, never gross. Gross burn understates runway, sometimes badly, and an understated runway drives panic decisions.
• Use current cash, not average cash. Runway is forward-looking and starts from the balance you have now.
• Wrap it so a cash-positive month does not produce nonsense: =IF(F2<=0,"cash positive",B13/F2). Dividing by a negative burn returns a negative runway, which is meaningless and looks like a spreadsheet error in a board pack.

Runway is also where the averaging window earns its keep. A twelve-month average smooths out an annual insurance payment or a quarterly tax bill. A three-month average taken across a quiet quarter can overstate runway by a third.

If the two averages disagree by a lot, that disagreement is the finding. Report both.

When to Use Which Burn Rate

Different questions want different variants, and using one figure for everything is how burn rate ends up in the wrong argument.

• Fundraising and board reporting: twelve-month net burn, plus the three-month figure if it is trending up. Investors will calculate the shorter window themselves, so pre-empt it.
• Hiring decisions: gross burn. A new salary adds to costs regardless of what revenue does, and gross burn is the number that new cost lands on.
• Pricing and unit economics: net burn per customer or per account, which means dividing net burn by active accounts in a separate column.
• Short-term cash management: a three-month rolling average, or weekly balances if the position is tight. At under three months of runway, a monthly average is too coarse to manage from.
• Scenario planning: build the burn figure as a cell other formulas reference, then change that one cell. This is where a spreadsheet beats a dashboard outright.

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Where the Excel Calculation Goes Wrong

The formula is easy. The data behind it is where the errors live.

Mixing accrual and cash figures. Pulling balances from the bank but expenses from an accrual-based P&L double-counts invoices booked but not yet paid. Pick cash or accrual and apply it to every column.

Averaging across a funding event. The most common single error. A funding round lands in the middle of the window, cash goes up, and the average comes out near zero or negative. Always strip non-operating cash in, as the D column above does.

Too short a window. Three months is an operational signal, not a planning figure. Anything presented as "our burn rate" without a stated window invites exactly the wrong follow-up question.

Ignoring timing within the month. A business that pays payroll on the 28th has a very different intra-month cash profile from one that pays on the 1st. Monthly burn rate cannot see this. If you are close to the edge, the monthly figure is not the right instrument at all.

Stale manual balances. A sheet updated by hand drifts. Note the date the balances were pulled in a cell next to the summary, so anyone reading it knows how old the number is.

Treating burn rate as a forecast. It is a measurement of the past twelve months. If you have just signed a large contract or cut a team, the historical figure describes a business that no longer exists. Rebuild from the months that reflect the current shape.

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Burn Rate in Excel vs the Alternatives

Accounting software reports. Xero, QuickBooks and the rest will produce a cash summary, and the data is more likely to be complete because it comes from the bank feed. What they will not do is let you change one assumption and see runway move. Use them as the source for column B and do the modelling in Excel.

A dedicated cash-flow tool. Worth it once you have multiple entities, multiple currencies, or a finance hire whose time is more expensive than the subscription. Below that, the tool mostly adds a login.

Google Sheets. Functionally identical for this calculation, and better if several people update the balances. Excel wins on large datasets and on scenario tools like Goal Seek and Data Tables, which are genuinely useful for runway modelling.

A one-off calculator on a website. Fine for a sanity check, useless for anything you need to revisit, because it keeps no history. Burn rate is only interesting as a trend.

The honest summary: Excel is the right tool for burn rate specifically because the number needs interpreting, and interpretation means changing assumptions and looking at what happens. That is what a spreadsheet is for.

Final Thoughts

Burn rate is one line of arithmetic sitting on top of data quality. The formula =(B2-B13)/12 will work the first time you type it. Whether the answer means anything depends on whether you pulled balances from the bank, stripped out funding, chose a twelve-month window, and labelled which burn rate you are quoting.

Build both variants, build runway as a formula rather than a number, and note the date the balances came from. Then the number survives being pasted into a board deck, which is where it is going.

If you are building out a wider set of models in the same workbook, What Is What-If Analysis in Excel? covers the scenario tools that turn a static runway figure into something you can actually plan against.

The number that matters is not this month's burn. It is whether it is going up.