Defining Burn Rate
Burn rate is the rate at which a startup is spending cash in excess of revenue. There are two important measures:
- Gross burn rate: Total monthly cash expenditures, regardless of revenue. If you spend $200K per month total, your gross burn is $200K.
- Net burn rate: Monthly cash expenditures minus monthly revenue. If you spend $200K and earn $80K, your net burn is $120K.
Net burn is the more useful metric for most purposes because it reflects the actual cash drain on the company. As revenue grows, net burn decreases even if spending remains constant.
Calculating Runway
Runway is simply cash on hand divided by monthly net burn rate. If you have $2.4M in the bank and a net burn of $120K per month, your runway is 20 months.
However, this simple calculation often understates the real situation because burn rate is rarely constant. Expenses tend to increase as companies hire and invest in growth. A more sophisticated approach projects monthly cash flows forward, accounting for planned hiring, seasonal revenue variations, and known upcoming expenses like annual software renewals or one-time costs.
Ideal Runway Targets
General guidelines for runway management:
- After a raise: Plan for enough runway to reach the next milestone after closing a funding round. This provides enough time to reach the next milestone and raise again with buffer for delays.
- Fundraising trigger: Start your next fundraise well before cash gets tight. Raising takes months, and you want buffer.
- Danger zone: A few months of runway left without an active fundraise is a critical situation that limits your negotiating leverage.
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Managing Burn Rate
Effective burn rate management involves:
- Monthly cash flow tracking: Review actual versus planned spending every month
- Headcount planning: Payroll is usually the largest startup expense. Hiring plans directly drive burn rate
- Milestone-linked spending: Increase spending only when you have validated the milestone that justifies it
- Scenario planning: Model what happens to runway if revenue grows slower than expected or a key deal falls through
Communicating Burn to Investors
Investors expect regular updates on burn rate and runway. Best practices include sharing a monthly financial summary that shows actual burn versus plan, current runway, key expense drivers, and revenue progress. Transparency builds trust, investors would rather hear about runway concerns early than be surprised by an emergency fundraise.
The Efficiency Equation
In the current market, investors increasingly evaluate burn efficiency: how much progress are you making per dollar burned? A company burning $150K per month that adds $50K in new MRR is far more capital-efficient than one burning $300K for the same MRR growth. Tracking and optimizing burn efficiency is as important as managing the absolute burn rate.