Bitcoin Stock-to-Flow Calculator
Free Bitcoin Stock-to-Flow Calculator. Evaluate Bitcoin scarcity with the S2F model and compare the real price with the model prediction.
Next Halving Impact
The S2F model is theoretical. Past correlation does not guarantee future prices. Use for educational purposes only.
How to use Bitcoin Stock-to-Flow Calculator
The Stock-to-Flow Calculator applies PlanB's scarcity model to Bitcoin. Enter the circulating supply and the annual new issuance (flow) — the calculator computes the S2F ratio, derives a model price from a power-law fit, and shows the percentage by which the live market price sits above or below that model line. It also projects the next halving's effect by halving the flow and recomputing the ratio and model price.
S2F quantifies how many years of current production it would take to double the existing supply. Higher ratios mean greater scarcity. After each Bitcoin halving, the flow is cut in half while stock continues to grow, mechanically doubling the ratio. The model has historically tracked BTC's macro price trajectory, though short-term deviations are common and expected.
Input guide and assumptions
Circulating supply is the total number of tokens currently in existence — for Bitcoin this is approximately 19.85 million as of April 2026. Annual production (flow) is the number of new coins mined per year: at 3.125 BTC per block and ~144 blocks/day, flow is approximately 164,250 BTC/year post-halving.
The calculator auto-fills Bitcoin's parameters but allows custom overrides for modeling other scarce assets (e.g., Litecoin, gold). The output includes the raw S2F ratio, the model price derived from the regression formula, the current market price, and the deviation percentage showing whether the asset trades above or below the model prediction.
How to interpret results correctly
The stock-to-flow ratio is simply existing supply divided by annual new issuance, so a reading of 56 means it would take roughly 56 years of current production to mine a quantity equal to today's circulating supply. Higher numbers signal greater scarcity. The model price is a power-law fit (price ≈ exp(3.21·ln(S2F) − 1.71)) that maps that ratio to a dollar figure — treat it as a historical curve, not a forecast.
The deviation row tells you how far the live price sits above or below that fitted curve: a positive percentage means the market trades richer than the model implies, negative means cheaper. Do not read this as a buy or sell signal. In 2022 the actual price fell more than 70% below the model line and stayed there, so a large gap is at least as likely to mean the model is wrong as the price. Pair it with our <a href="/mayer-multiple-calculator/">Mayer Multiple calculator</a> for a second, demand-aware lens.
Practical scenarios and planning workflow
Pre-halving modelling: with current supply near 19.8M and flow around 164,250 BTC/year, the calculator shows today's ratio and the projected post-halving ratio once issuance halves. Use it to visualise how the next reward cut roughly doubles stock-to-flow and lifts the model price on paper — a useful teaching exercise for understanding why supply shocks matter, paired with the <a href="/halving-calculator/">halving calculator</a> for exact dates and block rewards.
Post-halving review: after a halving actually occurs, update the flow figure to the new annual issuance (e.g. ~82,000 BTC/year after 2028) and compare the fresh model price against where Bitcoin really trades. This is where the model earns or loses credibility — repeated large gaps between the projected uplift and reality are the honest takeaway, not a price target to act on.
Risk and execution checklist
- Use it sensibly: 1) Confirm the supply figure matches a current source (around 19.8M and rising slowly toward the 21M cap). 2) Set flow to today's true annual issuance, not a stale pre-halving number. 3) Let the BTC price auto-fetch from CoinGecko or enter it manually. 4) Read the ratio first, the model price second, and the deviation last — in that order of reliability.
- After reading the output: write down the deviation and revisit it in a few weeks rather than reacting to one snapshot. If the model price is many multiples away from the actual price, that gap is the signal to distrust the model, not to bet on convergence. Cross-check the narrative against a chart-based tool like our <a href="/rainbow-chart-calculator/">rainbow chart calculator</a>.
Common mistakes to avoid
- The biggest mistake is treating the model price as a prediction. Stock-to-flow describes one variable — issuance scarcity — and ignores demand, regulation, liquidity, and macro entirely. From 2021 the live price diverged massively from the projected path and the original forecasts (six-figure floors) never materialised on schedule. Anyone sizing positions off the model number is trading a backward-looking curve fit, not a law of physics.
- A second error is ignoring demand altogether. Scarcity only raises price if buyers show up; gold has a stock-to-flow near 60 yet does not perpetually moon, which shows scarcity alone is not destiny. Also avoid using stale inputs — plugging a pre-halving flow into a post-halving world inflates the ratio and the model price artificially. Update both supply and flow before drawing any conclusion.
Performance benchmarks and expectation ranges
For context, Bitcoin's stock-to-flow has historically sat in the mid-50s to low-60s before a halving and roughly doubles afterward as issuance is cut in half. Gold's ratio is often cited around 60, the highest of the traditional monetary metals, while silver sits far lower near 20–30. These are reference points for intuition only — the calculator does not produce a gold or silver row, it just computes Bitcoin's own ratio.
On the model side, the fitted curve historically tracked Bitcoin's price within roughly an order of magnitude across multiple cycles, which is why it drew attention — but "within an order of magnitude" is a very loose fit for anything you would risk money on. Treat a deviation inside ±50% as the model being broadly in line, and anything beyond a few hundred percent as a sign the relationship has decoupled, as it did after 2022.
Execution templates you can reuse
A sensible review workflow is periodic, not reactive: check the ratio and deviation once a month or after major supply events rather than daily. Note the model price, the actual price, and the gap between them in a simple log. Over several readings you build a feel for how reliably (or not) the curve is tracking reality, which is far more honest than acting on any single deviation number.
Around halvings, run the calculator before and after the event using the projected post-halving flow, then revisit a few months later with real data. Comparing the projected uplift to the actual outcome is the most instructive use of the tool. For a broader "what changed" view of price scenarios, our <a href="/what-if/">what-if calculator</a> lets you model outcomes that do not depend on the S2F curve at all.
Data hygiene and model maintenance
Keep the inputs current. Bitcoin's supply grows every block, so refresh the supply figure occasionally toward the 21M ceiling, and reset the flow whenever a halving changes issuance — roughly every four years the annual mined amount halves. An outdated flow is the single most common reason the displayed ratio and model price drift away from anything meaningful.
Re-fetch the BTC price before reading the deviation, since the auto-fetched CoinGecko value can be a minute or two old during volatile sessions. If the fetch fails, enter a current price manually rather than leaving the field blank. Treat the whole exercise as educational housekeeping — a periodic scarcity snapshot — not a live trading dashboard.
Final validation before capital deployment
Sanity-check the model output against reality before you trust it. If the model price reads, say, ten times the actual market price, that does not mean Bitcoin is "due" to rise tenfold — it means the curve and the market disagree, and the market is the thing you can actually transact at. The model is the lens; the live price is the fact.
Validate the ratio itself with a quick mental check: supply divided by flow should land in the dozens for Bitcoin, not in the thousands or below one. If it looks wrong, you have likely entered flow in the wrong units (e.g. daily instead of annual). And remember the model lost credibility precisely because it kept being validated against price and kept failing after 2022 — so weight outside evidence over the curve.
Authoritative sources
Frequently asked questions
What is the Stock-to-Flow (S2F) model?
S2F divides existing supply (stock) by annual production (flow). For BTC post-2024 halving: stock 19.7M, flow 164k/year, S2F = 120. Plan B's formula projects price = exp(-1.84) * S2F^3.36, predicting $100k-$1M for the 2024-2028 cycle.
How accurate has Plan B's S2F model been?
S2F predicted BTC at $55k-$100k for 2020-2024, and BTC peaked at $73k (March 2024) and $99k (Nov 2024) - within range. However, the model failed in 2022 ($69k forecast vs $16k actual), so most analysts now treat it as one input, not a definitive valuation.
What's BTC's S2F ratio compared to gold and silver?
Gold S2F = 62 (197k tonnes stock, 3,200 tonnes/year), silver S2F = 22, BTC = 120 post-2024 halving (rises to 240 after 2028 halving). BTC overtook gold's scarcity in 2020 - the core "digital gold" thesis.
Why has S2F lost popularity since 2022?
The 2022 bear market saw BTC drop 75% while S2F predicted $100k+, breaking model fit. Critics (Vitalik Buterin, Nico Carter) argue S2F ignores demand-side factors. Plan B himself shifted to S2FX (cross-asset model) which has weaker statistical backing.
How is the cross-asset S2FX model different?
S2FX adds gold, silver, and diamonds as data points to extrapolate BTC's "phase transition" valuation, predicting $288k average for 2024-2028. The R² is high (0.99) but only 4 data points = severe overfitting risk. Use as narrative, not portfolio sizing.
Should I use S2F for trading decisions?
No - S2F has no intra-cycle predictive power and lags 6-18 months behind price. Pair it with on-chain metrics (MVRV, NUPL) and macro (DXY, rates). S2F works best as a multi-year supply-side anchor, not a tactical signal.
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