Altcoin Season Index A Simple Guide to Crypto Market Rotation

The cryptocurrency market moves in cycles. Sometimes Bitcoin gets most of the attention, while at other times money and interest spread across many different cryptocurrencies. When a large number of altcoins perform better than Bitcoin over a certain period, traders often describe the market as being in an altcoin season.

The altcoin season index is one of the popular ways to measure this change. Instead of looking at only one cryptocurrency, the index looks at how a group of major altcoins has performed compared with Bitcoin. The commonly used BlockchainCenter version checks the performance of the top 50 coins over a rolling 90-day period. When at least 75% of those coins outperform Bitcoin, the index classifies the market as an Altcoin Season.

This makes the altcoin season index useful for understanding market breadth. A single coin can rise sharply without meaning that the wider altcoin market is strong. The index tries to answer a broader question: are many major altcoins beating Bitcoin, or is Bitcoin still leading the market?

It is also important to understand that different websites can use slightly different methods. For example, CoinMarketCap uses a top-100 universe, while the BlockchainCenter version uses the top 50 and excludes stablecoins and certain asset-backed tokens. Therefore, two websites can sometimes show different readings on the same day.

This guide explains the altcoin season index in very simple language. We will look at how it works, how to read its numbers, why Bitcoin matters, what its limitations are, and how it can be used alongside other crypto market information.

How The Altcoin Season Index Works

The basic idea behind the altcoin season index is quite simple. It measures how many major altcoins have performed better than Bitcoin during a specific period.

The commonly referenced BlockchainCenter methodology uses the top 50 cryptocurrencies and compares their 90-day performance with Bitcoin. Stablecoins and asset-backed tokens are excluded because they are not designed to behave like normal speculative cryptocurrencies.

Imagine that 50 eligible cryptocurrencies are being examined. If 20 of them performed better than Bitcoin during the previous 90 days, the index would be around 40. If 35 performed better, the reading would be around 70. If 38 outperformed Bitcoin, the reading would be around 76.

The important point is that the index measures relative performance. An altcoin does not simply need to rise in price. It needs to perform better than Bitcoin during the measurement period.

For example, suppose Bitcoin rises 30% over 90 days. An altcoin that rises 20% has made a positive return, but it has not outperformed Bitcoin. Therefore, it would not count toward an altcoin-season reading under this methodology.

This difference is very important for anyone learning about the altcoin season index. People sometimes assume that altcoin season means every altcoin is going up. That is not necessarily true. Some altcoins may fall while others rise strongly. What matters for the index is how many of the eligible coins have beaten Bitcoin.

The 75% threshold is another important part of the common definition. A reading of 75 or higher means at least three-quarters of the tracked coins have outperformed Bitcoin during the previous 90 days. A reading of 25 or lower is generally classified as Bitcoin Season in the BlockchainCenter methodology. Readings between those levels are not classified as either extreme.

Because the calculation uses a rolling 90-day period, the number can change as new daily price data enters the calculation and older data leaves it. This means the altcoin season index should be viewed as a changing market indicator rather than a permanent label.

Understanding The Index Number Clearly

Learning to read the altcoin season index does not require complicated mathematics. The index is presented on a scale from 0 to 100, although the exact methodology can differ between providers.

A higher number means a larger share of the tracked altcoins has outperformed Bitcoin. A lower number means fewer altcoins have beaten Bitcoin.

The commonly used BlockchainCenter interpretation divides the scale into broad areas. Readings of 75 or higher indicate Altcoin Season, while readings of 25 or lower indicate Bitcoin Season. Values between 26 and 74 represent the middle area rather than a confirmed season.

Consider a few simple examples.

Suppose the index reads 20. This means the percentage of tracked altcoins outperforming Bitcoin is very low. The market is therefore closer to Bitcoin-led conditions.

Now imagine the index reads 45. This is much closer to the middle. Some altcoins are doing better than Bitcoin, but the broad market has not reached the conventional Altcoin Season threshold.

If the index reaches 60, more altcoins are beating Bitcoin. This can show that market participation has broadened, but it still does not meet the traditional 75 threshold.

At 75, the interpretation changes. Under the commonly used methodology, at least 75% of eligible coins have outperformed Bitcoin over the previous 90 days.

An index of 90 would indicate very broad outperformance among the tracked altcoins. However, even a very high reading does not guarantee that prices will continue rising. The number describes what has happened over the measurement period; it does not guarantee what will happen next.

This is one of the most important lessons when using the altcoin season index. It is a measurement tool, not a crystal ball.

Another important point is that the index does not measure the size of each coin's outperformance. Suppose 38 coins beat Bitcoin by a small amount. The index could still be around 76. If the same number beat Bitcoin by very large amounts, the index could also be around 76. The breadth is similar, even though the magnitude of returns is very different.

 

Therefore, users should look at the index together with price charts, trading volume, Bitcoin dominance, market capitalization, liquidity, and other relevant information.