This article provides general educational information about burn rate and cash runway calculation and does not constitute financial or business advice. Burn rate measures how quickly a startup spends cash each month, and cash runway estimates how many months the current cash balance can sustain that spend. This guide explains the standard formulas for gross burn, net burn, and runway, clarifies the gross vs net distinction, and walks through hypothetical worked examples that illustrate how each calculation is applied.
1. What Burn Rate and Runway Measure
Burn rate quantifies monthly cash outflow, while runway translates a cash balance into an estimated duration. Together they describe spending velocity and the time available at that velocity before additional cash is needed, assuming inputs remain constant. They do not predict future fundraising, revenue growth, or cost changes on their own.
Gross burn measures total monthly cash expenses regardless of revenue, which reflects the unadjusted spending pace. Net burn measures the net cash consumed after revenue is subtracted, which reflects the actual reduction in the cash balance each month. Runway then estimates months of cash remaining by dividing the current cash balance by monthly net burn. Like any single metric, each is most informative when evaluated alongside revenue trends, cost structure, and expected changes in both.
All three calculations assume a defined monthly period and consistent inputs for that period. This example assumes expenses and revenue are measured over the same month, and cash refers to readily available cash at the start of the period. This calculator estimates burn and runway using the same period-bound approach.
2. Gross Burn Rate Formula
Gross burn isolates total cash spent in a month before any revenue is considered. It is useful for understanding the absolute scale of monthly outflows and for comparing spending trends even when revenue fluctuates. The formula uses total monthly cash expenses for the period.
Gross Burn Rate = Total Monthly Cash Expenses
Where:
• Total Monthly Cash Expenses = All cash outflows in the month (salaries, rent, software, marketing, hosting, etc.)
• Excludes non-cash charges such as depreciation where the focus is cash consumed
• Measured over the same one-month window each periodThis example assumes total monthly cash expenses of $85,000, so gross burn is estimated as $85,000 per month. This calculator estimates gross burn from the expenses entered and does not constitute business advice about spending levels.
3. Net Burn Rate Formula
Net burn adjusts gross burn for cash inflows by subtracting monthly revenue or other cash receipts. It estimates the actual monthly decline in the cash balance when revenue partially offsets expenses. If revenue exceeds expenses, net burn can be zero or negative, indicating cash is not declining in that month under the assumed inputs.
Net Burn Rate = Total Monthly Cash Expenses − Monthly Revenue (Cash Inflows)
= Gross Burn − Monthly Revenue
Where:
• Total Monthly Cash Expenses = Same gross burn inputs as above
• Monthly Revenue = Cash collected from customers and other operating inflows in the same month
• Result is monthly cash consumed; if revenue exceeds expenses, net burn is negative (cash accumulating)This example assumes $85,000 in monthly expenses and $60,000 in monthly revenue, so net burn is estimated as $85,000 − $60,000 = $25,000 per month. This example assumes both inputs are measured in the same month and that revenue reflects cash collected, not recognized or invoiced amounts that may differ in timing. This calculator estimates net burn using the same subtraction applied to the values entered.
4. Cash Runway Formula
Cash runway estimates how many months the current cash balance can cover monthly net burn, assuming that net burn remains constant over the horizon. It is calculated by dividing the cash available at the start of the period by the monthly net burn for the period. The result is expressed in months and is sensitive to any change in either cash or net burn.
Cash Runway (months) = Current Cash Balance ÷ Monthly Net Burn Rate
Where:
• Current Cash Balance = Readily available cash at the start of the period
• Monthly Net Burn Rate = Total Monthly Cash Expenses − Monthly Revenue (from above), per month
• Assumes net burn remains constant; if net burn is zero or negative, runway is not meaningfully defined as a depletion timelineThis example assumes net burn is positive and stable for estimation purposes. If net burn were $25,000 and cash were $250,000, runway would be estimated as $250,000 ÷ $25,000 = 10 months. If net burn were zero in a given month under the assumed inputs, the cash balance would not be declining that month, and runway would not represent a countdown in that period. This calculator estimates runway using the same division and does not predict future revenue or expenses.
5. Worked Example: $250,000 Cash, $60,000 Revenue, $85,000 Expenses = 10 Months Runway
This example assumes a hypothetical early-stage startup to illustrate the arithmetic. The scenario is not based on a specific real business, and actual results will vary with pricing, customer mix, cost structure, and revenue timing. This calculator estimates runway using the same arithmetic applied to the values entered.
- Starting cash balance: This example assumes $250,000 in readily available cash at the start of the month. This figure is assumed to exclude restricted or non-liquid balances.
- Monthly expenses (gross burn): This example assumes $85,000 in total monthly cash expenses, including salaries, rent, software, marketing, and hosting. Gross burn is therefore estimated as $85,000 per month.
- Monthly revenue: This example assumes $60,000 in cash revenue collected in the same month from customers.
- Step 1: Calculate net burn — $85,000 − $60,000 = $25,000 net burn per month. This example assumes the expense and revenue inputs are measured over the identical monthly window.
- Step 2: Calculate runway — $250,000 ÷ $25,000 = 10 months of runway. This example assumes net burn remains constant at $25,000 each month; actual runway will vary if revenue or expenses change.
- Interpretation: This example assumes the startup would deplete the $250,000 balance in approximately 10 months at the assumed $25,000 monthly consumption, before considering any new revenue growth, cost changes, fundraising, or financing. If revenue rose or expenses fell, the same cash would be estimated to last longer, as shown in the next section.
If this example assumes revenue were $75,000 instead of $60,000 with expenses unchanged at $85,000, net burn would be estimated as $85,000 − $75,000 = $10,000 and runway as $250,000 ÷ $10,000 = 25 months, illustrating sensitivity to revenue. This calculator estimates the same thresholds from the inputs provided.
6. Gross vs Net Burn: How They Differ
Gross and net burn share the same expense base but answer different questions. Gross burn shows the absolute monthly spending pace, while net burn shows the net cash consumed after inflows. Reviewing both helps distinguish a change in spending from a change in revenue. The table below summarizes how each is defined and when it is typically reviewed.
| Dimension | Gross Burn | Net Burn |
|---|---|---|
| What it measures | Total cash spent per month | Cash consumed after revenue per month |
| Formula | Total Monthly Cash Expenses | Total Monthly Cash Expenses − Monthly Revenue |
| Revenue sensitivity | No — expenses only | Yes — falls when revenue rises, rises when revenue falls |
| Can be negative | No — expenses are cash outflows | Yes — negative when revenue exceeds expenses (cash increasing) |
| Best signal for | Scale and trend of spending | Actual monthly change in cash balance |
| Example at $85k expenses, $60k revenue | $85,000 per month | $25,000 per month |
This example assumes $85,000 in expenses and $60,000 in revenue. Gross burn remains $85,000 per month even as revenue changes, while net burn moves directly with revenue. This example assumes gross burn is most useful for cost control views and net burn is most useful for cash-duration views. This calculator estimates both from the values entered.
7. How Revenue Affects Runway
Because runway divides cash by net burn, and net burn is expenses minus revenue, any change in revenue changes runway even when cash and expenses are unchanged. Holding cash at $250,000 and expenses at $85,000 isolates the effect of revenue in the hypothetical scenarios below. This example assumes net burn remains constant at each revenue level for estimation purposes.
| Monthly Revenue (assumed) | Net Burn (Expenses $85k − Revenue) | Runway ($250k ÷ Net Burn) | Context |
|---|---|---|---|
| $40,000 | $45,000 | 5.6 months | Higher net burn shortens estimated runway |
| $60,000 | $25,000 | 10.0 months | Baseline from worked example |
| $75,000 | $10,000 | 25.0 months | Lower net burn extends estimated runway |
| $85,000 | $0 | Cash preserved (no depletion) | Revenue covers expenses; cash balance not declining that month |
| $95,000 | −$10,000 (net positive cash flow) | Not depleting (cash accumulating) | Revenue exceeds expenses; runway is not a countdown under these inputs |
This table illustrates why runway is not a fixed date but an estimate that depends on the net burn assumed for future months. This example assumes the same $250,000 starting cash and $85,000 expenses across rows; actual runway will vary with changes in both revenue and expenses over time. This calculator estimates runway by re-applying the same division to the values entered.
- Revenue growth extends runway: This example assumes revenue rises from $60,000 to $75,000 with expenses unchanged, net burn falls from $25,000 to $10,000 and runway is estimated to extend from 10 months to 25 months.
- Revenue decline shortens runway: This example assumes revenue falls from $60,000 to $40,000 with expenses unchanged, net burn rises from $25,000 to $45,000 and runway is estimated to fall from 10 months to about 5.6 months.
- Breakeven and beyond: This example assumes revenue of $85,000 equals expenses of $85,000, net burn is $0 and cash would not be declining that month. At $95,000 revenue, net burn is negative and the cash balance would be increasing, so a depletion runway is not meaningfully defined for that month.
8. Common Burn Rate Calculation Mistakes
Errors in burn rate and runway calculation often stem from mixing the wrong period, revenue definition, or cash scope into the formula. The table below summarizes frequent mistakes and the corresponding correct approach. Each correction reflects a general estimation practice; actual treatment may vary by business model.
| Mistake | Why It Is Wrong | Correct Approach |
|---|---|---|
| Using revenue recognized or invoiced instead of cash collected | Recognized revenue may not match cash timing and misstates net cash consumed | Use cash inflows collected in the same month as expenses for net burn |
| Annualizing or averaging without a monthly basis | Masks monthly variability and misstates months of runway | Calculate burn per defined month and divide cash by that monthly burn |
| Excluding relevant cash expenses (e.g., contractor costs, fees) | Understates gross burn and overstates runway | Include all cash outflows that reduce the cash balance in the period |
| Mixing gross and net burn interchangeably | Comparing total spend to net consumption distorts trend | Label and track gross and net separately; use net for runway |
| Treating runway as fixed when burn varies | Assumes constant spend and revenue that rarely hold | State the assumed net burn and re-estimate when inputs change |
| Using total cash including restricted funds | Overstates available balance and overstates runway | Use readily available cash at period start; note any restricted amounts separately |
Applying these corrections consistently across periods improves comparability. This calculator estimates burn and runway based on the cash, expenses, and revenue entered and does not constitute financial advice about cash management or fundraising strategy.
Frequently Asked Questions
- How do you calculate burn rate?
- This example calculates gross burn as Total Monthly Cash Expenses, and net burn as Total Monthly Cash Expenses − Monthly Revenue collected in the same month. For instance, this example assumes $85,000 in monthly expenses and $60,000 in monthly revenue, so gross burn is estimated as $85,000 and net burn as $85,000 − $60,000 = $25,000 per month. This calculator estimates burn using the same formulas applied to the values entered.
- How do you calculate startup runway?
- This example calculates runway as Current Cash Balance ÷ Monthly Net Burn Rate, with the result in months. For instance, this example assumes $250,000 in cash and $25,000 net burn per month, so runway is estimated as $250,000 ÷ $25,000 = 10 months. This example assumes net burn remains constant over the horizon; actual runway will vary if revenue or expenses change. This calculator estimates runway using the same division.
- What is the difference between gross burn and net burn?
- Gross burn is total monthly cash expenses before revenue, while net burn subtracts monthly revenue to estimate actual cash consumed. This example assumes $85,000 in expenses and $60,000 in revenue, so gross burn is $85,000 and net burn is $25,000. Gross burn does not change with revenue, while net burn falls when revenue rises and rises when revenue falls. This calculator estimates both from the values entered.
- What happens to runway if revenue changes?
- Because net burn is expenses minus revenue, runway moves inversely with revenue when cash and expenses are held constant. This example assumes $250,000 cash and $85,000 expenses: at $60,000 revenue, net burn is $25,000 and runway is 10 months; at $75,000 revenue, net burn is $10,000 and runway is 25 months; at $40,000 revenue, net burn is $45,000 and runway is about 5.6 months. This calculator estimates each scenario by re-applying the same formulas to the changed inputs.
- What is a good burn rate or runway for a startup?
- There is no universally good burn rate or runway; what is typical varies by stage, business model, fundraising context, and cost structure, and this article does not set targets or benchmarks. Burn and runway are estimates based on assumed monthly inputs and are most informative when reviewed alongside revenue trends, cost composition, and expected changes. This article provides general educational information and does not constitute financial or business advice.
- Can runway be infinite or what if net burn is negative?
- If net burn is zero in a month under the assumed inputs, the cash balance is not declining that month and runway does not represent a depletion countdown for that period. If revenue exceeds expenses, net burn is negative, indicating cash is accumulating rather than depleting. This example assumes $85,000 expenses and $95,000 revenue, net burn is estimated as −$10,000 and runway as a depletion timeline is not meaningfully defined. This calculator estimates net burn and runway from the inputs provided and does not predict future cash flows.