User Growth Trajectory Calculation

Objective

Build an Excel model that calculates a product's monthly user growth trajectory based on word-of-mouth marketing assumptions. The model needed to show when a given market cap would be reached, how fast growth would accelerate, and how sensitive the trajectory was to changes in key inputs.

Model structure

The model is structured in three layers:

Parameters: Adjustable inputs including initial user base, conversion behaviour distribution (immediate adoption, delayed adoption, or never), conversion timeframe (which week immediate converters act), influence factor (how many additional users each initial user influences per year), and total market cap for tracking saturation progress
Calculation: Month-by-month conversion calculations accounting for the full initial user base, the split across conversion behaviour types, and the compounding influence of each wave of adopters. "Yes" (immediate) users convert within the specified conversion week; "No" (delayed) users convert at a later stage based on the model parameters
Visualisation: A 12-month growth graph starting from the initial user base, showing trajectory toward market saturation and the point at which growth accelerates most sharply

Key outcomes

Fully adjustable model: any parameter can be changed and the trajectory updates across all calculations and charts instantly
Makes word-of-mouth growth assumptions explicit and testable, rather than leaving them implicit in planning documents
Market cap parameter allows saturation tracking, showing when growth will plateau under a given set of assumptions

Model walkthrough