What this shows
The Altcoin Season Index measures how broad an altcoin rally is: out of the 50 largest altcoins, what share did better than Bitcoin over the last 90 days.
- 75 or higher: Altcoin Season. Most large altcoins are beating BTC.
- 25 or lower: Bitcoin Season. BTC is beating most of them.
- In between: neither. Some altcoins lead, most don't.
The thresholds follow the widely used definition popularised by Blockchaincenter.
How it's calculated
Once a day:
- Take the top coins by market capitalisation from CoinGecko.
- Remove Bitcoin, stablecoins, and wrapped, staked or bridged tokens (for example WBTC or stETH), because they only mirror another asset's price. Keep the first 50.
- For each coin, compute the price change over the last 90 days and compare it with Bitcoin's change over the same period.
- Index = share of coins that beat BTC, from 0 to 100.
The history chart applies the same calculation to each day of the past year.
Limitations
- Survivorship bias. History uses today's top 50. Coins that were large a year ago and have since dropped out are not counted, which flatters past altcoin performance a little.
- Equal weight. A small top-50 coin counts as much as Ethereum. The index is about breadth, not about where the money is.
- A 90-day window lags. A rotation into altcoins shows up in the index only after it has been going on for a while.
How traders use it
- Rotation timing. A rising index from low levels suggests capital is starting to move from BTC into altcoins. A very high reading means many altcoins have already run.
- Portfolio balance. In a deep bitcoin season, holding a broad altcoin basket has usually lagged simply holding BTC.
- Context, not a signal. Combine it with the Crypto Fear & Greed Index and your own levels. Size positions with the position size calculator.
FAQ
What is altcoin season? A period when most major altcoins outperform Bitcoin. By this index's definition, at least 75% of the top 50 altcoins beat BTC over 90 days.
Is it altcoin season now? See the current reading at the top of this page. It updates daily.
Why are stablecoins and wrapped tokens excluded? Their price is pegged to the dollar or to another coin, so including them would distort the comparison with Bitcoin.
Why 90 days? It is long enough to filter out short pumps and short enough to reflect the current market phase. It is the standard window for this index.
Data for information only, not financial advice.