# What is Top-Down Forecasting? Definition & Technical Mechanics

> **Source:** [SPIDITS AI Startup & Venture Intelligence Glossary](https://spidits.com/startup-glossary)  
> **Category:** Metrics  
> **Canonical Citation:** [https://spidits.com/startup-glossary/top-down-forecasting](https://spidits.com/startup-glossary/top-down-forecasting)

## Definition
Top-Down Forecasting is a projection method that estimates future revenue by taking a percentage of the Total Addressable Market.

## Architectural Mechanics & Deep Dive
Top-Down Forecasting estimates revenue based on market share percentages. Because it lacks operational detail, founders use it for market opportunity discussions rather than detailed budgeting.

## Industry Applications & Real-World Use Cases
Initial market opportunity sizing and investor presentations

## Frequently Asked Questions

### Why do investors push back on top-down forecasting?
It assumes market share acquisition without explaining the specific sales and marketing actions required to win those customers.

### When is top-down forecasting useful?
During early ideation to evaluate whether a market is large enough to support a venture-scale startup.

## Related Terminology
- [financial-model](https://spidits.com/startup-glossary/financial-model)
- [revenue-projections](https://spidits.com/startup-glossary/revenue-projections)
- [bottom-up-forecasting](https://spidits.com/startup-glossary/bottom-up-forecasting)

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*From the SPIDITS AI Knowledge Base (311+ terms indexed). Explore full technical definitions: [https://spidits.com/startup-glossary](https://spidits.com/startup-glossary)*