Stock-to-Flow Says $500K. BTC Is $68K. Who's Wrong?

Stock to Flow Model Explained

The Stock to Flow (S2F) model, popularized by the pseudonymous analyst PlanB, measures scarcity by dividing the existing supply (stock) of an asset by its annual production rate (flow). Bitcoin's stock-to-flow ratio approximately doubles every four years at each halving event, as the flow (new Bitcoin mined per year) is cut in half. After the April 2024 halving, Bitcoin's S2F ratio increased to approximately 120, making it scarcer than gold by this metric.

PlanB's original 2019 model predicted Bitcoin prices based on a power-law relationship between S2F ratio and market capitalization. The model suggested Bitcoin should reach $100,000-$288,000 during the post-2024 halving cycle, with higher S2F values corresponding to higher prices. The mathematical simplicity and the model's accuracy in predicting the 2020-2021 cycle made it enormously popular among Bitcoin advocates.

The cross-asset S2F model extended the analysis by incorporating gold and silver data points, suggesting that Bitcoin follows the same scarcity-value relationship as precious metals. This broader framework strengthened the narrative that Bitcoin is a digital commodity whose value is fundamentally driven by supply scarcity rather than utility or network effects.

Understanding the model requires distinguishing between its descriptive and predictive claims. Descriptively, the S2F model correctly observes that Bitcoin's price has generally increased as its scarcity has increased through halvings. Predictively, the question is whether this relationship will continue to hold, which requires examining the model's assumptions and limitations.

Historical Accuracy Review

Feature	Description	Rating
Reliability	Consistent performance across conditions	High
Accessibility	Available to retail and institutional	Medium-High
Risk Profile	Manageable with proper position sizing	Variable

The S2F model's track record is mixed when examined honestly. It accurately predicted the general magnitude of the 2020-2021 bull market, with Bitcoin reaching $69,000 against a model prediction of $100,000-$288,000. While the peak fell short of the model's central prediction, the ballpark accuracy was impressive given the simplicity of the model.

However, the model has shown significant deviations. The predicted floor price of $100,000 by the end of 2021 was dramatically wrong, as Bitcoin traded at approximately $47,000. The subsequent drop to $15,500 in 2022 was over 80% below the model's predicted value for that period. PlanB acknowledged these deviations but attributed them to market cycles and external factors rather than model failure.

Statistical analysis reveals that the S2F model's apparent accuracy may be largely a result of both variables (price and S2F) trending upward over time. When you correlate two variables that both increase monotonically, you get a high R-squared value even if there is no causal relationship. This statistical critique is the most fundamental challenge to the model's validity.

The model's predictions for the current cycle will provide a significant test. If Bitcoin reaches $100,000-$200,000 as the S2F model suggests, it would strengthen the case for supply scarcity driving price. If Bitcoin peaks well below these levels despite the increased S2F ratio, it would suggest the relationship is weakening as the market matures and other factors become more important.

Major Criticisms and Flaws

The most fundamental criticism of the S2F model is that it ignores demand entirely. Supply scarcity is a necessary but not sufficient condition for high prices. An asset with zero demand has zero value regardless of how scarce it is. The S2F model implicitly assumes constant or growing demand, which is not guaranteed. A decline in Bitcoin adoption or a superior alternative could invalidate the model's predictions.

Ethereum's transition to proof-of-stake created a stock-to-flow ratio higher than Bitcoin's, yet ETH has not outperformed BTC as the model would predict. This counter-example suggests that S2F is not the primary driver of value in cryptocurrency. Other factors like network effects, utility, institutional adoption, and narrative strength appear to be at least equally important.

The model lacks a theoretical mechanism explaining why the specific power-law relationship should hold. Unlike economic models grounded in supply-demand theory, the S2F model is purely empirical, fitting a line to historical data without a rigorous explanation for why the relationship exists. Empirical models without theoretical backing are more likely to break down as conditions change.

PlanB's response to criticisms has evolved over time, with newer model versions incorporating additional variables like time and network effects. However, each modification reduces the model's simplicity, which was its original appeal. A more complex model that accurately predicts price is useful, but it is no longer the elegant supply-scarcity story that captured the crypto community's imagination.

Alternative Valuation Models

The Network Value to Transactions (NVT) ratio compares Bitcoin's market cap to its on-chain transaction volume, similar to a price-to-earnings ratio for traditional assets. High NVT suggests the price is unsupported by network activity, while low NVT suggests undervaluation. This model incorporates demand-side data that S2F ignores, making it a useful complement.

Metcalfe's Law models value Bitcoin based on the square of its active user base, grounded in network theory. As more users join the Bitcoin network, the value of the network increases exponentially. This model has shown reasonable accuracy in predicting Bitcoin's broad price trajectory and provides a theoretical framework (network effects) that S2F lacks.

The production cost model values Bitcoin based on the electricity and hardware costs required to mine a block. Since miners are the primary sellers in the market, the cost of production creates a natural floor price. When Bitcoin trades below production cost, miners shut down, reducing sell pressure and creating conditions for price recovery. This model is useful for identifying cycle bottoms but less useful for predicting peaks.

Realized value and MVRV models compare Bitcoin's current market cap to its realized cap (the sum of all coins valued at their last movement price). When the MVRV ratio exceeds historical peaks (above 3.5-4), the market is historically overvalued. When it falls below 1, the market is undervalued. This model uses on-chain data to assess relative valuation without making specific price predictions.

S2F 2026 Price Prediction

The current S2F model predicts Bitcoin should be trading in the $100,000-$300,000 range during 2026 based on the post-halving S2F ratio of approximately 120. With Bitcoin currently around $92,000, the model suggests significant upside potential if the historical relationship holds. However, this prediction carries all the caveats discussed in the criticisms section.

A more conservative interpretation of S2F uses it as one input among many rather than a standalone price predictor. Combined with on-chain metrics (MVRV at 2.1, suggesting room to run), ETF flow data (strong and growing), and technical analysis (constructive chart structure), the convergence of multiple models supports a bullish outlook for the balance of the cycle.

The key insight from the S2F model is directional rather than precise: Bitcoin's programmatic scarcity increase through halvings creates a supply shock that, when met with stable or growing demand, tends to push prices higher. The exact price target is less important than the directional bias this creates for long-term positioning.

For practical trading purposes, we recommend using S2F as a macro backdrop that supports a long-term bullish thesis, not as a short-term trading signal. Combine it with cycle analysis, on-chain metrics, and technical analysis for timing entries and exits. The best approach is to be positioned for the S2F-predicted upside while having risk management in place for the possibility that the model's accuracy deteriorates.

For more insights, explore our guides on Trading Strategies and Risk Management.

Frequently Asked Questions

What does the Stock to Flow model predict for Bitcoin?

The S2F model predicts Bitcoin should trade in the $100,000-$300,000 range during 2026, based on the post-halving S2F ratio of approximately 120. However, the model has shown significant deviations from predictions in recent years, and its purely supply-based approach ignores demand dynamics. Use S2F as one input among many rather than a standalone prediction.

Is the Stock to Flow model accurate?

The S2F model was broadly accurate for the 2020-2021 cycle in terms of magnitude but missed the timing and specific price levels. The model predicted $100,000 as a floor price that was never reached. Statistical critics argue the correlation may be spurious since both variables trend upward. Treat S2F as a directional indicator of scarcity impact rather than a precise price forecaster.

What are alternatives to the Stock to Flow model?

Alternative Bitcoin valuation models include Metcalfe's Law (network value based on users), the NVT ratio (market cap vs transaction volume), MVRV Z-Score (market value vs realized value), and production cost models. Each captures different aspects of Bitcoin's value proposition. Combining multiple models provides a more robust valuation framework than relying on any single model.