Cash Burn Rate: Calculation And Forecasting

What Is Burn Rate?

Burn rate is the amount of cash a business spends each month, net of any revenue it brings in. It tells you how fast the cash balance is shrinking, and for any business that is not yet covering its costs from operations, it is the number that determines how long the money lasts.

How It's Calculated

There are two versions, and knowing which one you are looking at matters.

Gross burn rate is total cash spent in a month, before accounting for any revenue:

Gross Burn Rate = Total Monthly Cash Outflows

Net burn rate is the monthly decrease in the cash balance after revenue is factored in:

Net Burn Rate = Monthly Cash Outflows - Monthly Cash Inflows

A pre-revenue business has identical gross and net burn rates because there is no incoming cash to offset spending. A business generating some revenue but not yet profitable will have a lower net burn than gross burn, and the gap between the two narrows as the business grows toward breakeven. Once a business is cash flow positive, net burn becomes zero or negative, at which point the term no longer applies in the same way, since the balance is growing rather than shrinking.

Most investors and founders focus on net burn because it reflects the actual rate at which the bank balance is declining. Gross burn is more useful internally for understanding the total cost base, independent of how much revenue is coming in.

Worked Example

A software startup has been operating for six months. It has three full-time employees, a product team on contract, and is paying for cloud infrastructure and office space. Monthly outflows total $68,000. The business has early customers generating $12,000 in monthly recurring revenue, which is collected reliably each month.

• Gross burn rate: $68,000 per month

Net burn rate: $68,000 - $12,000 = $56,000 per month

The business currently holds $420,000 in the bank.

At the current net burn rate, cash runway is $420,000 / $56,000 = 7.5 months.

Now suppose the team closes two new enterprise contracts worth a combined $18,000 in additional monthly revenue starting next month. Net burn drops to $68,000 - $30,000 = $38,000. With the same opening balance of $420,000, runway extends to just over 11 months. The cost structure did not change at all; the revenue did.

That sensitivity is the reason burn rate and runway need to be tracked together, not in isolation.

Why It Matters in Practice

It sets a hard deadline for every major decision

When the cash balance divided by net burn gives you seven months, every decision that costs money has to be weighed against that timeline. Hiring, a new marketing spend, a tool subscription, each one either extends or shortens the runway. Burn rate does not make those decisions for you, but it makes the cost of each decision concrete. A founder who knows the monthly burn rate can express any proposed expense in terms of runway consumed, which changes how the decision is made.

It is the number investors actually use

When an investor asks about runway, they want to know burn rate and current cash balance, not a qualitative account of how things are going. Gross burn tells them the total cost structure. Net burn tells them how quickly the business needs more money. The ratio of the two tells them something about revenue traction. A business that cannot answer these questions precisely in a fundraising conversation is at a disadvantage, and the imprecision itself sends a signal.

It tracks the effect of every operational change

Burn rate is a monthly number, which means it updates fast enough to reflect decisions made in the business: a new hire, a contract cancelled, a revenue line that stops converting. Watching it month over month shows whether the business is moving toward breakeven or drifting further from it. A burn rate that is holding steady while revenue grows is a business gaining ground. One that is climbing while revenue stays flat is a business shortening its own runway.

How Burn Rate Affects Your Cash Flow

Burn rate is how fast you spend cash each month. Divided into your balance, it is your runway, the clearest deadline a founder has.

That deadline is not static. Every month the revenue line changes, every cost decision made or deferred, every invoice collected early or late, all of it moves the number. A business tracking burn rate only quarterly is working with a figure that may already be considerably wrong by the time it is reviewed. Monthly tracking is the minimum, and for businesses within six months of running out of cash, the calculation should be updated more often than that.

The relationship between burn rate and the cash flow forecast is direct. Burn rate describes what has been happening; the forecast shows what happens next if current patterns continue, or if planned changes take effect. A team planning to hire two engineers in Q2 can run the forecast with and without those hires and see exactly what the bank balance looks like in six months under each scenario. That is not a complicated exercise, but it is one that requires current, accurate cash flow data rather than a rough mental model of monthly spending.

How You'd See This in Cash Flow Frog

Cash Flow Frog connects to QuickBooks Online, QuickBooks Desktop, Xero, and Sage Intacct and builds a rolling cash flow forecast automatically from your accounting data. QuickBooks records what happened. Cash Flow Frog projects what is coming.

Because the forecast pulls from live accounting data and updates as the books update, the monthly cash position reflects actual inflows and outflows rather than a manually maintained spreadsheet that goes stale between updates. If you want to trace a specific cost, a payroll run, a contractor invoice, a subscription charge, the tool drills down to the transaction level. For businesses with multiple entities or currencies, the forecast runs natively across all of them, up to three years out. Burn rate and runway are two sides of the same calculation; the related entry at cashflowfrog.com/glossary/cash-runway/ covers how runway is derived from burn and what it means for planning.

Related Terms

• Cash Runway
• Net Burn Rate
• Gross Burn Rate
• Operating Cash Flow
• Cash Flow Forecast
• Working Capital