Last updated: Aug 18, 2026
Base Net Burn is your Net Burn minus variable customer acquisition costs (CAC). It isolates the operational burn your business carries independent of growth investment, showing whether the business could survive without growth spending.
A SaaS company has a Net Burn of $500,000 per month and spends $600,000 per month on variable customer acquisition costs.
Base Net Burn = $500,000 - $600,000 = -$100,000
A negative result means the core business is already cash-flow positive. Cutting variable marketing spend would eliminate the burn entirely, though it would also stop growth.
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Visualize your base net burn by month in a line chart - this view will let you easily observe changes in the trend.
Base Net Burn
Base Net Burn
Most burn rate metrics bundle growth spending with core operating costs. That makes it hard to separate what you must spend from what you choose to spend.
Base Net Burn solves that problem. By stripping out variable CAC, it answers a direct question: if you stopped acquiring new customers tomorrow, would the business survive?
That insight matters most when capital is scarce, growth slows, or investors want to see a credible path to sustainability. It also helps founders and finance teams understand how much of their burn is discretionary versus structural.
The sign and magnitude of Base Net Burn tells you a lot about your options:
You have two options when calculating Base Net Burn:
| CAC type | What it includes | Best used when |
|---|---|---|
| Variable CAC | Paid media, performance marketing | You want to model a fast lever you can pull immediately |
| Total CAC | Marketing spend plus sales and customer success headcount | You want a complete picture of acquisition cost |
Variable CAC is usually the right starting point. It reflects what you can turn down quickly, without restructuring the team or breaking long-term commitments.
Base Net Burn pairs naturally with Net Burn and LTV/CAC Ratio when evaluating how long you can operate under different spending scenarios.
If your Base Net Burn is negative, your runway is theoretically unlimited as long as you're willing to stop growing. That's a meaningful data point when negotiating with investors or deciding whether to raise a bridge round.
If your Base Net Burn is positive, the gap between it and your Net Burn tells you how much time variable CAC cuts would buy. Combined with your total funding available and Customer Acquisition Cost payback period, you can model realistic survival scenarios without guessing.
The metric is most useful during periods of uncertainty: when growth is slower than expected, when a fundraise is taking longer than planned, or when the board is asking hard questions about capital efficiency.
