How to Build a Financial Model
A step-by-step guide to creating a financial model for your business.
How to Build a Financial Model
A financial model is a way to "see the future" of a business before it happens. It shows: what will happen with money, where the bottlenecks are, when the company will become profitable, and what decisions really drive the economy.
This note offers a simple, practical approach that works for small businesses, startups, and even complex projects. Without Excel acrobatics and complicated terms.
1. Start with Assumptions—the Foundation of the Model
A financial model is built not on numbers, but on assumptions. Numbers are just a consequence.
What's included here:
- Demand and market: how many clients you can attract monthly.
- Price: how much you sell for.
- Costs: fixed (office, salaries) and variable (cost of goods or an hour).
- Conversions: how funnel stages turn into money.
- Growth rates: what will increase and why.
Example: You have an online service. The assumptions might be: — traffic: 10,000 people per month; — conversion to registration: 12%; — conversion to payment: 4%; — average check: 1,200 ₽; — churn: 6% per month.
Small changes in these parameters change the outcome significantly—so first, talk them out "in words," and only then put them in a table.
2. Model Structure: What It's Made Of
Keep the structure simple: three sheets are enough in 90% of cases.
Revenues
We determine how money enters the company:
- sales by month;
- subscriptions and renewals;
- additional services;
- average check and its dynamics.
The main idea is to link revenue to user actions. Not "we will earn this much," but "clients do X → this yields Y."
Costs
We divide into two groups:
- Fixed: rent, team salaries, licenses, admin.
- Variable: cost of a unit of goods/deal, payment commission, delivery.
Simple test: if sales = 0 → what costs remain? That's fixed.
Cash Flow
This is a mirror of reality:
- when money comes in;
- when it goes out;
- how much is needed for survival;
- and if there is a safety margin.
Unexpected discoveries almost always arise on this sheet. For example, a business is profitable, but it hits a cash gap in the 4th month.
3. Unit Economics: Checking if the Product Makes Sense
Unit economics shows whether it's profitable for you to attract and retain one client.
Mini-formulas:
CAC (customer acquisition cost) =
advertising expenses / attracted clients
LTV (lifetime value) =
average payment × number of payments
Margin = (revenue - variable costs) / revenue
If LTV < CAC → the business is either dying or turning into a hobby with an expensive entry ticket.
4. Assembling the Model: Step-by-Step Algorithm
- Write down the initial assumptions. Clearly and without optimism. Optimism in models is the main enemy.
- Build a forecast for users/sales. Use a funnel: traffic → leads → sales.
- Calculate revenues by month. Link to the number of clients and the average check.
- Add costs. Fixed by month, variable—for each sale.
- Build a cash flow. Simple rule: cash is more important than profit.
- Check scenarios. Minimum, realistic, optimistic.
- Find control points. Where does modeling show the greatest effect?
5. What the Model Shows Besides Numbers
A good financial model is not just "how much we will earn." It answers more important questions:
- When will the cash run out if nothing changes?
- What costs can be cut without pain?
- What sales volume is needed to reach operating profit?
- What happens if the price drops by 10%?
- How many people need to be hired and when?
If the model doesn't help make a decision—it's not a model, it's a pretty table.
📌 Checklist: "Is My Financial Model Adequate?"
- [ ] All assumptions are described in words, not just numbers.
- [ ] Revenues are linked to user actions.
- [ ] Fixed and variable costs are not mixed.
- [ ] There is a cash flow—not just a P&L.
- [ ] Scenarios are built: minimum, realistic, growth.
- [ ] Unit economics are adequate: LTV ≥ 3×CAC (or at least 1.5× for a start).
- [ ] The formulas are understandable to you tomorrow, not just today.
- [ ] The main growth levers are highlighted.
If at least three points are not covered—the model needs to be refined.
🧮 Mini-Calculator (logic to insert into Excel/Notion)
Clients per month = Traffic × Conversion to lead × Conversion to sale
Revenue = Clients × Average check
Gross Profit = Revenue - (Clients × Variable costs per unit)
Unit Economics:
LTV = Average check × Number of repeat payments
CAC = Marketing expenses / New clients
LTV/CAC = LTV / CAC
Break-even point:
BEP = Fixed costs / Margin
Copied—and you can model this evening.
Short Conclusion
A financial model is not about "guessing the future." It's a thinking tool: it allows you to see the system, understand the levers, remove illusions, and make decisions soberly.
Think about how the described approach applies to your business: where are your key drivers, which assumptions are the most fragile, and what from the model should be checked in reality this week.
When the model works—the business becomes more transparent, and decisions calmer.