“How long will our cash last?” is one of those questions that can quietly haunt even the most capable founder or small business owner. The good news is you do not need a fancy model to answer it. You need two numbers you can pull from your bank statements and bookkeeping: your burn rate and your cash runway.
In this article, I will define burn rate and net burn in plain English, show you a quick monthly calculation with a realistic example, then turn that burn rate into a clear runway estimate you can actually make decisions with.
What burn rate means (and why it matters)
Burn rate is a measure of cash movement. Depending on context, it can mean either:
- Gross burn: how much cash you spend in a month
- Net burn: how much your cash balance declines in a month
Most people use burn rate to answer one core question: How many months can we keep operating before we run out of money?
You will usually hear burn rate discussed as a monthly number, like “we burn $25,000 per month.” That is not just a metric for startups chasing venture capital. It is also a practical tool for:
- Service businesses with uneven client payments
- Ecommerce brands that buy inventory upfront
- Trades and local businesses with seasonal slowdowns
- Any owner making hiring, lease, or equipment decisions
Burn rate matters because it turns vague stress into a measurable timeline, and timelines are what good decisions are built on.
Gross burn vs net burn (the two definitions you need)
People sometimes use “burn rate” loosely, so let us make it crisp. One note up front: the definitions below are cash-based and designed for founders and small business owners using bank and card activity. Investor and VC reporting sometimes uses narrower definitions (for example, excluding inventory or debt principal). For operating decisions, cash-based clarity is usually what you want.
Gross burn
Gross burn is your total cash outflows per month. This is what actually left your bank accounts (and what you paid on cards, if you track it that way). It often includes things like payroll, rent, software, contractors, marketing, insurance, and taxes paid.
Depending on your business, you may also include inventory purchases and loan payments because they are real cash outflows. If you want extra clarity, split gross burn into:
- Operating spend (payroll, rent, tools, marketing)
- Working capital and inventory (inventory buys, changes in receivables)
- Debt and financing related outflows (loan principal and interest)
If you spend $80,000 in cash in a month, your gross burn is $80,000.
Net burn
Net burn is the amount your cash balance actually drops per month after accounting for cash coming in.
The simplest way to think about it:
Net burn = Cash outflows − Cash inflows
If you spend $80,000 but collect $65,000, your net burn is $15,000. That means your bank balance is shrinking by about $15,000 per month.
If cash inflows are higher than outflows, you do not have net burn for that period. Some people call that negative net burn. Either way, it means you are cash flow positive for that month.
Sanity check: net burn should roughly match the change in your cash balance for the period (beginning cash minus ending cash). If it does not, look for internal transfers between accounts, owner draws, loan proceeds, or other one-time items that you may have mixed in.
How to calculate burn rate in minutes (a simple monthly method)
If you have never modeled runway before, start with this simple approach. You can do it in a spreadsheet or even on paper.
Step 1: Pick the time period
Use one month to start. Once you are comfortable, use a 3 month average to smooth out weird timing (annual insurance, one-time equipment, quarterly taxes).
Step 2: Total your cash outflows
Look at what actually left your bank accounts and credit cards during the month. Include:
- Payroll and contractor payments
- Rent and utilities
- Software subscriptions
- Marketing spend
- Insurance
- Loan payments (principal and interest)
- Taxes you actually paid
- Inventory purchases (if applicable)
- Equipment and other large one-time purchases (include them, but consider labeling them separately)
A quick note: your accounting Profit and Loss statement is helpful, but it is not the same as cash movement. Burn rate is about cash.
Important credit card note: do not double count. Use one source of truth. Either (1) include card charges as outflows, or (2) include the monthly card payment as the outflow, but not both.
Loan payment note: principal repayment reduces cash but is not a P&L expense. Interest is an expense. This is one of the most common reasons profit and cash look different.
Step 3: Total your cash inflows
Add up cash that came in:
- Customer payments collected
- Platform payouts (Stripe, Shopify, Amazon, app stores)
- Any other operating income received in cash
Be careful not to count new debt or investment as “revenue.” For burn, it is fine to track financing, but keep it in its own line so you know whether the business itself is funding operations.
Also exclude internal transfers between your own accounts. Moving $10,000 from savings to checking is not an inflow. It is just cash shifting pockets.
Step 4: Compute net burn
Net burn = Outflows − Inflows
If the result is positive, you are burning cash. If it is negative, you generated cash that month.
A real example: burn rate and net burn
Let us say a small B2B services company has the following in April.
April cash outflows
- Payroll (2 employees): $28,000
- Contractors: $7,500
- Rent and utilities: $4,200
- Software and tools: $1,300
- Marketing: $3,500
- Insurance: $600
- Loan payment: $1,400
- Taxes paid: $1,000
Total outflows (gross burn): $47,500
April cash inflows
- Client retainers collected: $30,000
- Project invoices paid: $11,000
Total inflows: $41,000
Net burn
Net burn = $47,500 − $41,000 = $6,500 per month
That means, at this pace, the business bank balance drops by about $6,500 each month.
How to convert burn rate into cash runway
Cash runway is how long your cash will last if your net burn stays the same.
The basic formula:
Runway (months) = Cash on hand ÷ Net burn
Using the example above, if the business has $78,000 in the bank and a net burn of $6,500:
Runway = $78,000 ÷ $6,500 = 12 months
That is a usable answer. But you can make it even more decision-friendly with a few upgrades.
Upgrade 1: Use a 3 month average net burn
If your net burn was $2,000 in February, $9,000 in March, and $6,500 in April, your 3 month average is:
Average net burn = ($2,000 + $9,000 + $6,500) ÷ 3 = $5,833
Then runway becomes:
$78,000 ÷ $5,833 ≈ 13.4 months
Upgrade 2: Subtract “do not touch” cash first
Some cash is not truly available to fund operations, like sales tax you collected, payroll tax reserves, or a minimum cash buffer you need to sleep at night.
If you decide you need a $15,000 buffer that you will not spend, then:
Usable cash = $78,000 − $15,000 = $63,000
Runway = $63,000 ÷ $6,500 ≈ 9.7 months
Notice how the story changed. Same business, same month, but now you have a clearer sense of what is actually safe.
Upgrade 3: Adjust for seasonality and known changes
If the next quarter is predictably weaker, a backward-looking average can be too optimistic. In seasonal businesses, it is often safer to estimate runway using your worst typical month, or a simple forward plan that reflects what is coming (a slow season, a planned hire, a lease increase, or an expiring contract).
Common burn rate mistakes
Mixing profit with cash
You can be profitable on paper and still burn cash because of timing, especially with large receivables, inventory buys, or debt payments.
Double counting credit cards
If you include credit card charges as outflows and also include the credit card payment, you will overstate burn. Pick one method and stick to it.
Letting transfers distort your numbers
Moving money between your own accounts is not an inflow or outflow for burn. Exclude internal transfers so your totals reflect real spending and real collections.
Ignoring payment timing
If customers pay you 45 days after you invoice, your “runway” depends on collections, not sales. Track accounts receivable aging if you invoice clients.
Mini-example: if you booked $50,000 in sales but only collected $30,000 this month, your inflows are $30,000. The other $20,000 might arrive next month or it might arrive late. Runway cares about what hits the bank.
Forgetting one-time or annual bills
Annual software renewals, quarterly estimated taxes, and insurance premiums can cause sudden drops. If they are predictable, build them into a monthly average. If they are one-time investments (like equipment), include them in cash tracking but consider separating them from your “operating burn” so you can see what is repeatable.
Counting financing as operating health
Loans and investor cash can extend runway, but they do not fix a leaky business model. Keep your operating net burn separate from “financing inflows” so you know what is really happening.
When to cut costs vs raise capital
This is where burn rate becomes more than a math exercise. It becomes a decision tool.
Rule of thumb: these ranges vary by industry, volatility, and how predictable your sales are, but they are useful for many small teams.
Cut costs when:
- Your runway is under 6 months and there is no clear near-term cash inflection (signed contracts, product launch, seasonal peak).
- Your biggest expenses are not tightly tied to revenue (for example, tools you do not use, extra space, unfocused marketing, “nice to have” hires).
- You can reduce spend without breaking delivery quality or customer trust.
Owner-friendly approach: start with expenses that create the least customer pain. Renegotiate software, pause experiments, tighten contractor scopes, and review every recurring charge.
Raise capital or financing when:
- You have a repeatable way to turn cash into growth (for example, you spend $1 on acquisition and reliably get $3 back over time)
- Your bottleneck is timing, not demand (for example, big receivables, inventory cycles, or a long enterprise sales cycle)
- You are cutting costs so deeply that it would damage the core engine of the business (sales capacity, fulfillment, product quality, compliance).
In plain terms: raising money makes sense when it is fueling a working machine, not when it is keeping a broken one running.
If you feel stuck
If you have 9 to 12 months of runway, you usually have time to test improvements (pricing, collections, retention, marketing efficiency) without panic. If you have under 6 months, prioritize decisive action: cut burn fast, accelerate collections, and explore funding in parallel.
A quick runway checklist
- Pull the last 3 months of bank and card activity.
- Total monthly cash outflows (avoid credit card double counting).
- Total monthly cash inflows from customers (exclude internal transfers).
- Compute net burn for each month and the 3 month average.
- Sanity check net burn against the change in your cash balance.
- Decide on a minimum cash buffer.
- Runway = (Cash on hand − Buffer) ÷ Average net burn.
- Pick one action to extend runway this month: cut a cost, raise prices, speed up collections, or improve retention.
FAQ
What is a “good” burn rate?
A good burn rate is one that is intentional and funded. Burning $5,000 per month with 3 months of runway is risky. Burning $50,000 per month with 24 months of runway and strong unit economics can be perfectly rational.
Should I use gross burn or net burn for runway?
Use net burn to calculate runway because runway is about how fast your cash balance is shrinking. Gross burn is still useful for cost control, especially if revenue is lumpy.
What if my net burn changes every month?
That is normal. Start with a 3 month average, then add notes for known changes (a hire starting next month, a contract ending, a loan payoff). You can also build a “best case, base case, worst case” runway by changing inflows and outflows.
Is burn rate only for startups?
No. Any business with fixed costs, seasonality, inventory, or uneven payment timing benefits from understanding burn and runway. It is simply cash planning, with clearer language.
The bottom line
Burn rate is not a vanity metric. It is a clarity metric. Once you know your net burn and your runway, your next steps become much more grounded: either extend the runway (cut costs, improve collections, adjust pricing) or secure more fuel (financing or investment) with a specific timeline in mind.
If you want the simplest starting point, remember this: Runway (months) = Usable cash ÷ Net burn. Calculate it once, and you will never look at your bank balance the same way again.
