Bitcoin Stock-to-Flow Model (AUD)
PlanB's Stock-to-Flow model for Bitcoin, fitted to AUD-priced monthly closes. The S2F ratio (Bitcoin's stock divided by annual flow of new issuance) is computed deterministically from the halving schedule. The model fits a log-log line between S2F ratio and market cap. The chart shows model-predicted price alongside actual BTC AUD price, with the deflection (how far above or below model) highlighted. The model has been controversial since 2021 - actual price has materially diverged from predictions during the current cycle.
Chart
PlanB's Stock-to-Flow model (white dashed line) plotted against actual BTC AUD monthly closes (gold solid line). The S2F ratio is computed deterministically from Bitcoin's halving schedule. The model is re-fitted to AUD market cap on every site build. Hover any point on the chart for the exact actual price, model price, S2F ratio, and deflection for that month.
What is the current Stock-to-Flow deflection?
Deflection is the percentage difference between actual BTC AUD price and the S2F model's predicted price for the same month. As of the most recent month, Bitcoin sits well below the S2F model's prediction - the model's post-2024-halving forecast called for BTC at A$400,000+ AUD by end-2025, while actual BTC AUD ended 2025 at approximately A$207,000. The hover tooltip on the chart shows the exact deflection for every month.
Historical context: the model fit closely with actual price during 2014-2020 (deflections typically within ±30%) but has consistently overshot since mid-2021. PlanB has acknowledged the divergence and proposed a revised model ("S2FX") that fits cross-asset rather than time-series data, but the canonical S2F model continues to be the most-cited version.
Bitcoin Stock-to-Flow ratio at each halving
| Halving | Date | Block reward (BTC) | S2F ratio (post-halving) |
|---|---|---|---|
| Genesis | Jan 2009 | 50 | ~0 (very low stock, very high flow) |
| 1st | Nov 2012 | 25 | ~28 |
| 2nd | Jul 2016 | 12.5 | ~56 |
| 3rd | May 2020 | 6.25 | ~56 |
| 4th (current) | Apr 2024 | 3.125 | ~120 |
| 5th (est.) | Apr 2028 | 1.5625 | ~240 |
| 6th (est.) | Apr 2032 | 0.78125 | ~480 |
For reference: gold's stock-to-flow ratio is approximately 60. Silver's is approximately 22. Bitcoin overtook gold's S2F at the April 2024 halving - PlanB's original thesis was that this should drive BTC's market cap toward gold's (~$13 trillion USD), implying BTC prices well above A$1 million per coin. The current cycle has not validated that thesis.
Does the Stock-to-Flow model still work?
Materially no, as a quantitative forecast. As a directional intuition (more scarce = more valuable), it remains useful. The model has had four distinct phases:
- 2014-2017: Tight fit. Pre-S2F-publication, in-sample fit.
- 2018-2020: Tight fit. The model's first major validation.
- 2021: Brief over-shoot then sharp divergence. Bitcoin peaked at ~A$94k in November 2021 vs the model's A$130k+ prediction for end-2021.
- 2022 onwards: Material under-shoot. Bitcoin has tracked 30-70 percent below the model's predictions throughout the 2022-2025 period.
The cleanest critique is that S2F treats scarcity as if it deterministically caused price, but actual price reflects demand factors S2F ignores: macro liquidity, ETF flows (a 2024-era development), regulation, narrative cycles, and bull-market participation rates. The model's pre-2021 fit relied heavily on the 2017 parabolic peak as an anchor; subsequent cycles have not produced equivalent spikes. Treat the chart as cycle reference, not as a price target.
What is the Stock-to-Flow model?
The Stock-to-Flow model is a scarcity-based valuation framework originally developed for commodities (gold, silver, platinum) and adapted to Bitcoin by pseudonymous analyst PlanB in March 2019 (the "Modeling Bitcoin's Value with Scarcity" Medium article). The core thesis:
- Stock = currently-circulating supply.
- Flow = annual new issuance.
- S2F ratio = stock / flow. Higher = scarcer.
- The model: ln(market cap) = slope * ln(S2F) + intercept. Fits log-log relationship between S2F and market value.
- Prediction: as Bitcoin's halvings double the S2F ratio, the model predicts roughly 4x market cap increase per halving (slope ≈ 3.3).
The model's appeal was simplicity: a single deterministic time series (S2F) predicting Bitcoin's market value over multi-year horizons. Its weakness was the same: ignoring all demand-side factors. The 2022-2025 divergence has been the model's most significant real-world test, which it has failed quantitatively.
Methodology
- Stock-to-Flow ratio. Computed deterministically from Bitcoin's halving schedule. Stock = cumulative block rewards from genesis to date. Flow = current block reward * 144 blocks/day * 365 days. Both numbers are publicly known and don't require external data.
- Market cap. Computed for each historical month as actual BTC AUD close * circulating supply at that month.
- Fit. Ordinary-least-squares linear regression on (log10(S2F), log10(market cap)) using all historical monthly data points. Produces slope, intercept, and residual standard deviation.
- Model price. For any month: predicted market cap = 10 ^ (slope * log10(S2F) + intercept). Predicted price = predicted market cap / supply at that month.
- AUD-native. All inputs in AUD throughout. The fitted slope and intercept differ slightly from PlanB's USD-fitted version due to AUD's long-term depreciation against USD.
- Resilience. Halving schedule is deterministic (never breaks). Only the price input needs refreshing on each build. If the price source is unreachable, the previous data file is preserved.
Where the model breaks down
- Failed since 2021. Actual BTC price has materially diverged from S2F predictions for 4+ years. Quantitative usefulness as a forecast is low.
- Ignores demand factors. Macro liquidity, ETF flows, regulation, adoption rate, narrative cycles all affect price; S2F treats them as zero.
- Small sample. Only 4 completed halvings to fit, and the pre-2021 fit was anchored heavily by the 2017 parabolic peak.
- Halving-day discontinuity. The S2F ratio steps up sharply at each halving, but the model predicts a smooth curve - the discontinuity creates artefacts in the residuals.
- AUD-specific. The AUD-fitted slope differs from PlanB's USD slope. Comparisons to other published S2F charts should account for the FX-driven difference.
Related tools
- Bitcoin Logarithmic Regression Bands (AUD) - alternative long-run BTC valuation model using time-based regression rather than scarcity-based.
- Bitcoin Rainbow Chart (AUD) - sentiment-labelled version of the log regression.
- Bitcoin Risk Metric (AUD) - 0-1 cycle positioning score from the log regression.
- Bitcoin Pi Cycle Top Indicator (AUD) - mechanical cycle-top crossover signal.
- Bitcoin Halving Countdown - days to the next halving + cycle performance overlay.
- Charts Dashboard - all cycle indicators on one page.
- Crypto CGT Calculator - apply the ATO 50 percent discount to any Bitcoin disposal.
Frequently asked questions
The Stock-to-Flow (S2F) model is a Bitcoin price-prediction model published by pseudonymous analyst PlanB in March 2019. It hypothesises that Bitcoin's market value follows a power-law relationship with its scarcity (stock-to-flow ratio). The model fits ln(market value) = slope * ln(S2F ratio) + intercept on historical data. Because Bitcoin's flow halves every 210,000 blocks (~4 years), the S2F ratio rises sharply at each halving, predicting price increases. The model was widely cited in 2019-2021 but has materially diverged from actual price since mid-2021.
Materially no, since mid-2021. PlanB's model predicted Bitcoin at $100,000+ USD by end-2021 and $288,000 by 2024. Actual prices were significantly lower at those dates. PlanB himself has acknowledged the divergence and proposed a revised 'S2FX' model. The original S2F retains pedagogical value (it captures the directional intuition that scarcity drives long-run price) but its quantitative predictions have failed. Treat as a historical reference rather than a forward forecast - which is how this chart presents it.
Bitcoin's Stock-to-Flow ratio is approximately 120 as of mid-2026 (after the April 2024 halving). For comparison: pre-2012-halving S2F was ~25; pre-2016-halving was ~50; pre-2020-halving was ~25 (re-set briefly by the halving); pre-2024-halving was ~56. The next halving (April 2028) will roughly double the S2F ratio again to ~240. Gold's S2F ratio is approximately 60. Silver's is approximately 22. Bitcoin's S2F has now exceeded gold's, which PlanB cited as evidence that BTC should command a comparable monetary premium.
Several reasons cited by critics and supporters: (1) The model treats stock-to-flow as if it deterministically caused price, but actual price reflects demand factors that S2F ignores (macro liquidity, ETF flows, regulation, narrative cycles). (2) The pre-2021 fit had only 3 halving cycles to fit, which is too few data points for confident projection. (3) The 2022 macro environment (Fed tightening, banking crisis, FTX collapse) introduced supply-demand shocks not captured in the model. (4) PlanB's original logarithmic fit relied heavily on the 2017 peak as an anchor; subsequent cycles have not produced equivalent parabolic spikes.
Stock-to-Flow ratio = current circulating supply / annual new issuance. For Bitcoin: stock = sum of all block rewards mined to date; annual flow = current block reward * 144 blocks per day * 365 days. Both numbers are deterministic from Bitcoin's halving schedule, so the S2F ratio can be plotted as a known time series with no data dependency. This chart computes the ratio at each historical month, then fits PlanB's log-log model against actual BTC AUD market cap to derive AUD-specific model parameters.
PlanB's original S2F model was fitted to USD prices. This chart re-fits the same functional form to AUD-priced monthly market caps so the model output is in AUD rather than USD. The fitted slope and intercept differ slightly from the USD version due to AUD's long-term depreciation against USD, but the directional and cycle interpretations are equivalent. Australian-resident investors care about AUD-denominated portfolio value, so the AUD-fitted model is the correct reference.
The fit refits on every site build using the latest available BTC AUD monthly closes. The S2F ratio time series is deterministic (computed from the halving schedule) so it never needs refreshing. Only the price input needs to be fresh; the model parameters re-derive automatically. If the upstream price source is unreachable, the previous static price dataset is preserved and the model continues to render.
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