How to Build a Burn and Revenue Projection: How Many Months Out to Model

Every founder building a cash projection asks the same question eventually: how far out should I model this? Too short and you cannot see a problem coming. Too long and you are just making up numbers with more decimal places.

There is a practical answer. It depends on two things: what you are using the projection for and how predictable your revenue is right now.

What Owners Get Wrong

The most common mistake is building a 24-month projection when the business has been operating for eight months and has no recurring revenue. The numbers in months 13 through 24 are not forecasts. They are guesses dressed up in a spreadsheet. Worse, people make decisions based on them.

The other mistake goes the other direction. Some owners build a 90-day rolling view and nothing else. That is fine for cash management, but it does not tell you whether you can afford to hire someone in six months or whether you will run out of money before the next revenue milestone.

The fix is not a single magic horizon. It is matching the horizon to the purpose of the model.

The CFO Perspective: Match Horizon to Use Case

Here is how to think about it. There are three common reasons to build a burn and revenue projection:

Operational cash management: You need to know if there is enough money in the account to cover payroll and suppliers next month. For this, 13 weeks (three months) is the standard. Weekly granularity. Update it every week. This is your operational model.

Hiring and spend decisions: You want to know if you can afford to add a person, sign a lease, or make a significant purchase in the next six to twelve months. For this, a 12-month model is the right tool. Monthly granularity. The detail needs to be reasonably grounded in known contracts, pipeline, and committed costs.

Fundraising or investor conversations: Investors want to understand the path to a milestone, usually 18 to 24 months. The further out you go, the more your model relies on assumptions rather than facts. That is expected. The key is being explicit about what the assumptions are. Do not hide them.

Consider a simple example. A services business with 80% recurring revenue and eight known contracts can credibly model 12 months out. The revenue side is real. The burn is mostly known. A pre-revenue startup with three pilot clients cannot credibly model 12 months of revenue. They can model 12 months of burn and show different revenue scenarios with clearly labeled assumptions. That is still useful. It just has to be honest about what is known versus assumed.

What to Do About It

1. Decide what the model is for before you build it. Cash management, hiring decisions, and investor conversations need different models. Do not try to use one spreadsheet for all three.
2. Start with 12 months as your default operating horizon. It is long enough to catch problems early and short enough that your inputs are grounded in something real. Monthly columns, starting with the current month.
3. Build the burn side first. Fixed costs are knowable. List every committed expense: payroll, rent, software, debt service. These numbers are accurate. Build them in detail before touching revenue.
4. Separate known revenue from projected revenue. Signed contracts and active retainers go in one bucket. Expected deals or renewals go in another. Label them clearly. The sum of the two is your revenue line, but the first bucket is firm and the second is a forecast.
5. Add a 13-week cash view as a separate tab. Your 12-month model handles planning. Your 13-week view handles operations. Both are necessary. Neither replaces the other.
6. Update the model monthly, not annually. A projection that is 11 months old is not a forecast. It is history with some guesses attached. Lock in actuals each month and roll the projection forward.
7. If you are using the model for fundraising, extend to 18 months and add a scenario tab. Show base, upside, and downside. Label the key assumptions driving each one. Investors do not expect you to be right. They expect you to understand the drivers.

How Confident Should You Be in Each Part

A good rule of thumb: the first three months should be 80-90% accurate if you update consistently. Months four through twelve should be directionally correct, meaning the trend and the order of magnitude are right. Anything beyond 12 months is a scenario, not a forecast, and should be treated that way in conversations.

This does not mean months 13 through 24 are useless. They are useful for answering questions like: "At what point does the business need new revenue to remain solvent?" or "If we close two more deals, when does cash flow turn positive?" Those are valuable questions. Just do not present the answers as precise predictions.

If you are building this for the first time or want someone to pressure-test the assumptions before you use it to make a real decision, book a free call at peterxiacpa.com/book.

Next step: see it in your free Instant CFO Snapshot.