Bitcoin Stock‑to‑Flow Model Explained: How Scarcity Drives Price

Bitcoin’s stock‑to‑flow (S2F) model links the cryptocurrency’s limited supply to its price, offering a scarcity‑based forecasting tool that some analysts treat like a commodity valuation metric [2]. The model, first popularized by pseudonymous analyst “Plan B” in 2019, calculates a ratio of existing coins to newly minted coins and projects a “fair” price based on that figure [2].

Key takeaways

• The S2F ratio equals Bitcoin’s circulating supply divided by its annual inflation, currently about 53.9, implying 53.9 years of production to match the existing stock [2].
• Plan B’s formula Model Price = exp(-1.84) × SF^3.36 yields a model price of roughly $104,480 for today’s ratio [2].
• The model’s 463‑day smoothing window stems from dividing a halving cycle (210,000 blocks) into three phases and averaging over daily block production [2].
• Critics note that Bitcoin’s price still behaves like a high‑volatility asset, with a correlation of ~0.53 to the stock market and often underperforming in market downturns [1].
• Financial advisors typically recommend limiting Bitcoin to 1‑5 % of a portfolio because its volatility can dominate overall risk [1].

How the Stock‑to‑Flow Ratio Is Built

The S2F metric uses two components: “stock,” the total circulating Bitcoin (about 19.19 million coins), and “flow,” the yearly issuance of new coins (approximately 356,000, derived from 975 BTC mined per day) [2]. Dividing stock by flow gives the ratio, which for Bitcoin today is roughly 53.9, meaning it would take over five decades of mining to produce the current supply [2]. The flow figure changes with mining difficulty, network congestion, hardware costs, and the scheduled halving events that cut the block reward roughly every four years [2].

From Ratio to Price Prediction

Plan B’s model translates the S2F ratio into a price estimate using the exponential formula exp(-1.84) × SF^3.36. Applying the current ratio of 53.9 produces a model price near $104,480, which sits above Bitcoin’s actual market price at the time of writing [2]. The model’s price line is plotted against real market data, allowing analysts to see whether Bitcoin is trading above or below its “fair” value [2]. To smooth short‑term fluctuations, the model averages data over a 463‑day window—a period derived from halving cycles and the typical three‑phase price pattern (bull run, correction, mean reversion) observed after each halving [2].

Why It Matters

The S2F model frames Bitcoin as a scarce commodity akin to gold, reinforcing the narrative that limited supply can drive long‑term price appreciation [2]. However, real‑world performance shows Bitcoin behaving more like a high‑risk tech asset than a safe‑haven store of value; its correlation with equities is moderate (~0.53) and it often falls harder than stocks during market crashes [1]. Consequently, many financial advisors suggest a modest allocation—typically 1‑5 % of total net worth—to capture potential upside without letting Bitcoin’s volatility dominate a portfolio [1]. As the next halving approaches, the S2F ratio will rise, potentially widening the gap between model and market prices and keeping the debate over its predictive power alive.