How to build a financial model for a startup

A financial model tells, in numbers, how your startup will earn and spend money. Early-stage forecasts are not expected to come true exactly; investors want to see how well you understand the business and how consistent your assumptions are.

Structure

A good model has a few linked sheets:

1. Assumptions: all inputs in one place
2. Revenue: customers, price, growth and churn
3. Costs: people, marketing, infrastructure, overheads
4. Cash flow: monthly inflows, outflows and cash balance
5. Summary: annual revenue, gross margin, net loss or profit, runway

Setting assumptions

• Base every assumption you can on real data: conversion rates, revenue per customer, churn.
• Where you lack data, use industry benchmarks and note the source.
• Build growth by channel rather than one "X percent a month": visitors, trial starts, paid conversions.

See our startup metrics guide for definitions.

Revenue

Build bottom-up: new customers + existing − churned = customers at period end, multiplied by average revenue. Model price rises and plan upgrades separately; see our pricing guide.

Costs

• Hiring plan: start month and cost for each role. Usually the biggest item.
• Marketing: consistent with acquisition cost.
• Infrastructure and tools: costs that change with usage
• Add inflation and currency effects as separate assumptions.

Scenarios

Prepare optimistic, realistic and pessimistic cases. Knowing how long cash lasts even in the pessimistic case is one of the most important outputs; see our cash flow guide.

Presenting to investors

• Share the detailed model in the data room; show only the summary in the deck.
• Show the next 18–24 months monthly and later years annually.
• Link the round to the milestones it will reach in the model.
• Avoid exaggerated "hockey stick" curves; unexplained jumps reduce trust.

Common mistakes

• Burying assumptions inside formulas
• Confusing cash flow with the income statement (forgetting collection delays)
• Underestimating non-people costs

Conclusion

A financial model is a tool for running the company, not a one-off document. Compare it with actuals monthly and update assumptions. Keep it consistent with your business plan.