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 page load. 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. For October 2026 it is -45.4 percent: the model says A$216,582, the market says A$118,282. At the end of 2025 the model stood at A$214,052 against an actual close of A$131,255. The hover tooltip on the chart shows the exact deflection for every month.
Historical context: because this chart refits the model to the whole AUD history, including the weak post-2024 period, the line runs through the middle of the data rather than along PlanB's original curve. Deflection swung between -79 and +339 percent from 2014 to 2020, and between -61 and +229 percent since 2022. The price sat mostly above the refit line from 2018 to 2023 and has been below it since the April 2024 halving doubled the S2F ratio. 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 | ~8 |
| 2nd | Jul 2016 | 12.5 | ~24 |
| 3rd | May 2020 | 6.25 | ~56 |
| 4th (current) | Apr 2024 | 3.125 | ~120 |
| 5th (est.) | 2028 | 1.5625 | ~250 |
| 6th (est.) | 2032 | 0.78125 | ~500 |
For reference: PlanB put gold's stock-to-flow ratio at about 62 and silver's at about 22. Bitcoin overtook gold's S2F at the April 2024 halving. PlanB's original thesis was that matching gold's scarcity should push BTC's market value toward gold's, implying prices far above today's. 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: Wide swings around the refit line, from about 80 percent below it to more than 300 percent above in the 2017 blow-off. PlanB published in 2019, so this is all in-sample.
- 2018-2023: Price mostly above the refit line, because the model only steps up at halvings while price kept rising between them.
- April 2024: The halving doubled the S2F ratio overnight, lifting the model price with it.
- Since then: Price below the model through 2025 and 2026, -45.4 percent at the latest month. PlanB's original USD model, fitted before 2021, overshot by far more.
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 a jump in market value. PlanB's original slope of about 3.3 implied roughly a 10x rise per halving; the AUD refit on this chart currently gives a slope of 2.65, about 6.3x per doubling.
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, which happens automatically every day: monthly closes from January 2013 derived from Bitstamp BTC/USD converted at the daily AUD/USD rate, with Kraken's native BTC/AUD market for the last two years. If a price source is unreachable, the previous data file is kept.
Where the model breaks down
- Poor forecaster. PlanB's original USD model missed badly after 2021, and even refitted to all AUD data the model sits -45.4 percent from price at the latest month. 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.
Not as a forecast. PlanB's original model implied an average price around US$100,000 for the 2020-2024 halving period, and his later S2FX variant around US$288,000; Bitcoin did not reach those levels in that period. 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.
About 122 at block 969,696 (3 October 2026): 20.09 million BTC in circulation against 164,250 new BTC a year (3.125 BTC × 144 blocks × 365 days). The ratio steps up at each halving: from about 4 to 8 at the 2012 halving, 12 to 24 in 2016, 28 to 56 in 2020 and 60 to 120 in 2024. The 2028 halving will take it to roughly 250. PlanB put gold at about 62 and silver at about 22, so Bitcoin's S2F has been above gold's since the 2024 halving. The chart itself uses a simplified 144-blocks-a-day supply model, which currently reads 117.
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 is recomputed on every page load using the latest BTC AUD monthly closes, which refresh automatically every day. 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 a price source is unreachable, the previous data file is kept and the model continues to render.
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