The stock-to-flow (S2F) ratio measures scarcity. You divide the amount of an asset that already exists (the stock) by the amount produced in a year (the flow). The answer is roughly how many years of current production it would take to rebuild the existing supply. On figures available on 25 October 2026, Bitcoin's ratio is about 122 and gold's is about 61. The Bitcoin S2F price model goes one step further. It assumes market value rises with that ratio, and it is the work of one pseudonymous analyst, PlanB. The model matched Bitcoin's price from 2019 to early 2022 and then diverged sharply. The ratio is plain arithmetic, while the price forecast is a contested hypothesis.
The formula
S2F = stock ÷ annual flow
- Stock: the total supply in existence.
- Flow: the new supply added over one year. For gold that is mine production. For Bitcoin it is the new coins miners receive in each block's generation transaction.
A high ratio means new supply is small compared with what already exists. A low ratio means new supply can quickly dilute existing holdings.
Worked example: Bitcoin vs gold, October 2026
Bitcoin
- Stock. Blockchain.com's total-supply endpoint reported 20,103,268 BTC on 25 October 2026.
- Flow. Since the April 2024 halving, each block pays a subsidy of 3.125 BTC. One block every ten minutes gives 144 blocks a day, so 3.125 × 144 × 365 = 164,250 BTC a year.
- Ratio. 20,103,268 ÷ 164,250 ≈ 122.
Blocks do not arrive exactly every ten minutes, so the real flow differs a little from the theoretical figure. This is why charting sites show slightly different S2F values.
Gold
- Stock. The World Gold Council puts total above-ground gold at 222,600 tonnes as of the end of Q2 2026.
- Flow. The council reports 2025 mine production of 3,671.6 tonnes, a narrow record that it says may be revised.
- Ratio. 222,600 ÷ 3,671.6 ≈ 61.
By this measure Bitcoin's new supply is now about half as large, relative to its existing stock, as gold's.
How halvings move the ratio
The Bitcoin block subsidy halves every 210,000 blocks, which is roughly every four years. The total supply approaches, but never quite reaches, 21 million BTC. The Bitcoin Wiki estimates the last fraction will be issued around 2140. Each halving cuts the flow in half while the stock barely changes, so the ratio roughly doubles overnight.
| Halving | Block height | Date | Subsidy after | Stock at halving | S2F after (approx.) |
|---|---|---|---|---|---|
| 1st | 210,000 | 28 Nov 2012 | 25 BTC | 10,500,000 | 8 |
| 2nd | 420,000 | 9 Jul 2016 | 12.5 BTC | 15,750,000 | 24 |
| 3rd | 630,000 | 11 May 2020 | 6.25 BTC | 18,375,000 | 56 |
| 4th | 840,000 | 20 Apr 2024 | 3.125 BTC | 19,687,500 | 120 |
The stock and ratio columns are calculated from the issuance schedule with the theoretical 144 blocks a day. They are not measured market data.
The next halving falls at block 1,050,000 and cuts the subsidy to 1.5625 BTC. At the current pace of blocks, that points to roughly the first half of 2028. The ratio would then rise to about 250. This is an estimate, and the date moves with block times.
Work out Bitcoin's stock-to-flow ratio
Enter a coin supply, a block subsidy and a pace of blocks to see the S2F ratio the article's formula gives.
| Bitcoin in existence (stock) | Block subsidy paid to miners | Blocks mined per day | Stock-to-flow ratio (years of current issuance to rebuild the stock) |
|---|---|---|---|
| 20,103,268 BTC | 3.125 BTC | 144 blocks | 122.4 |
| 19,687,500 BTC | 3.125 BTC | 144 blocks | 119.9 |
| 18,375,000 BTC | 6.25 BTC | 144 blocks | 55.9 |
| 15,750,000 BTC | 12.5 BTC | 144 blocks | 24 |
- Annual flow is block subsidy × blocks a day × 365, the theoretical issuance used in the article; it leaves out the effect of uneven block times.
- The worked examples use the stock at the 4th, 3rd and 2nd halvings from the article's table, which are calculated from the issuance schedule rather than measured market data.
This only measures supply scarcity: it has no demand term and does not forecast price, and real trackers differ slightly because of block times and smoothing.
From ratio to price: PlanB's model
The ratio describes supply. The price claim comes from a 2019 Medium article, "Modeling Bitcoin's Value with Scarcity", by an analyst writing as PlanB (@100trillionUSD). According to Coin Bureau's summary, PlanB ran a linear regression of Bitcoin's market value against its S2F on 111 data points from 2009 to 2019. Coin Bureau reports an R² of 95% and a projected market value of about $1 trillion after the 2020 halving.
In 2020 PlanB published an extension called S2FX (stock-to-flow cross-asset). It put Bitcoin, silver and gold on one curve and treated Bitcoin's history as a series of "phases". FXStreet reported on 1 July 2020 that the model focused on a Bitcoin price of $288,000 for the period up to the 2024 halving. With S2F at 56, that phase implied a market value of around $5.5 trillion.
Both versions come from a single author and were never independently replicated in a peer-reviewed publication. That should weigh on how much you trust any price line drawn from them.
Where the model broke
- The 2022 divergence. By June 2022, Bitcoin's price was far below the S2F model line. On 21 June 2022 Ethereum co-founder Vitalik Buterin wrote that "stock-to-flow is really not looking good now". He added that "financial models that give people a false sense of certainty and predestination that number-will-go-up are harmful". PlanB replied the same day that after a crash "people are looking for scapegoats". Both posts were reported by Decrypt and The Block.
- Correlation is not cause. Nico Cordeiro of Strix Leviathan called S2F a "chameleon model", meaning it looks convincing until you look closely, as summarised by Coin Bureau. Grayscale cautioned that the relationship may be spurious and does not account for demand.
- Supply only. The formula has no demand term. Rate changes, forced selling and new buyers all sit outside it.
- Few observations. Only four halvings have happened, so any fit to halving cycles rests on very little independent data.
- New demand channels. On 10 January 2024 the US SEC approved the listing and trading of spot bitcoin exchange-traded products. SEC Chair Gary Gensler stressed that the agency "did not approve or endorse bitcoin". Demand of this kind comes in on its own schedule, which has nothing to do with the issuance timetable.
Using S2F sensibly
- Use the ratio as a fact about supply. It tells you how fast new coins dilute existing ones, and it is fully predictable from the code.
- Treat the model price line as a hypothesis. Charting sites still plot it, but the 2022 gap showed it can be wrong by a wide margin for a long time.
- Pair it with demand-side measures. Glassnode defines MVRV as market cap divided by realized cap, the value of coins at the price they last moved on-chain. In Glassnode's guidance, values above 3.5 have generally marked late bull phases, and values below 1.0 mean much of the supply is held near break-even or at a loss. The Mayer Multiple is price divided by its 200-day moving average. Glassnode notes that values of 2.4 and 0.8 have historically coincided with overbought and oversold conditions. These levels are historical patterns, not rules.
- Check the inputs. Different trackers use different smoothing windows and supply data, so treat small differences between them as noise.
Limitations: the S2F figures above are calculated from public supply data on the stated dates, and neither the ratio nor the model predicts future prices. This article is not investment advice.
