What Is Altcoin Season and How the Altcoin Season Index Works
Altcoin season is when most top altcoins outperform Bitcoin. Learn how the Altcoin Season Index is calculated and how to use it without common mistakes.
Key points
- Altcoin season is a market phase where most top altcoins outperform Bitcoin over a set period.
- The Altcoin Season Index tracks the share of top 50 coins (excluding stablecoins and wrapped tokens) that beat Bitcoin over 90 days.
- A reading of 75 or higher suggests altcoin season, while 25 or lower points to Bitcoin season.
What is altcoin season?
Altcoin season is a period when most major cryptocurrencies other than Bitcoin (called altcoins) rise faster than Bitcoin. It is not a formal event with a start date. It is a pattern that traders and analysts describe after looking at price performance over a set window, usually 90 days.
During altcoin season, money that was in Bitcoin often moves into smaller coins, and prices across the market can rise together. The opposite phase is sometimes called Bitcoin season, when Bitcoin outperforms most altcoins.
Why the Altcoin Season Index exists
It is easy to say “altcoins are pumping” or “Bitcoin is dominating,” but those statements are opinions. The Altcoin Season Index turns that idea into a number. It measures how many of the top 50 cryptocurrencies (by market value) have beaten Bitcoin over the past 90 days.
The index is published by Blockchain Center, a crypto data and research platform. It is designed to be a simple, objective gauge of market rotation, not a trading signal.
How the Altcoin Season Index is calculated
The core calculation is straightforward:
- Take the top 50 cryptocurrencies by market capitalization.
- Exclude stablecoins (like USDT or USDC) and wrapped tokens (like WBTC), because their prices are designed to stay near a fixed value and would distort the result.
- For each remaining coin, compare its price change over the last 90 days to Bitcoin’s price change over the same 90 days.
- Count how many coins outperformed Bitcoin.
- Divide that count by the total number of coins in the group, then multiply by 100 to get a percentage.
That percentage is the index value. For example, if 40 of the 50 coins (after exclusions) beat Bitcoin over 90 days, the index would be 80.
What the numbers mean
| Index reading | Interpretation |
|---|---|
| 75 or higher | Altcoin season: most top altcoins are outperforming Bitcoin. |
| 25 to 74 | Mixed or neutral: no clear winner between Bitcoin and altcoins. |
| 25 or lower | Bitcoin season: Bitcoin is outperforming most top altcoins. |
These thresholds are conventions used by the index provider. They are not rules set by any regulator or exchange.
A practical example
Imagine it is September 29, 2026. Suppose the top 50 list includes 45 coins after removing stablecoins and wrapped tokens. If 30 of those 45 coins have gained more than Bitcoin over the past 90 days, the index would be (30 / 45) × 100 = 66.7, which falls in the neutral zone. If 38 coins beat Bitcoin, the index would be 84.4, signaling altcoin season.
You can track this yourself by pulling 90-day price data for the top 50 coins and Bitcoin from a public data source, then running the same comparison. Many crypto data sites publish the index directly, so you do not have to calculate it manually.
How to use the index without overreacting
- Treat it as a thermometer, not a forecast. The index tells you what has already happened over the past 90 days. It does not predict what comes next.
- Check the date. The index updates regularly. A reading from last month may not reflect today’s market.
- Look at the trend. A single reading is less useful than watching whether the index is rising or falling over several weeks.
- Combine it with other information. Bitcoin dominance, trading volume, and news can all help you understand the context.
Risks and common mistakes
1. Treating altcoin season as a guarantee
Even during a strong altcoin season, individual coins can fall. The index measures the group, not every member. A high reading does not mean every altcoin will go up.
2. Ignoring Bitcoin’s role
Altcoin season is defined relative to Bitcoin. If Bitcoin’s price drops sharply but altcoins drop less, the index can still rise. That does not mean altcoins are in a healthy uptrend; it may just mean they fell less.
3. Chasing performance
Buying an altcoin simply because it outperformed Bitcoin over the past 90 days is a classic mistake. Past performance does not guarantee future results. By the time the index shows altcoin season, much of the move may have already happened.
4. Forgetting about liquidity and risk
Many altcoins have thinner trading volume than Bitcoin. That can make it harder to buy or sell at the price you see, and prices can move sharply on small trades. Altcoins also carry higher risks of failure, including project abandonment or regulatory issues.
5. Misreading the exclusions
Stablecoins and wrapped tokens are removed from the calculation. If you try to recreate the index yourself and leave them in, your number will be wrong. Always check which coins are included.
Summary
Altcoin season is a market phase where most top altcoins outperform Bitcoin. The Altcoin Season Index measures this by comparing the 90-day price performance of the top 50 cryptocurrencies (excluding stablecoins and wrapped tokens) to Bitcoin. A reading of 75 or higher suggests altcoin season, while 25 or lower suggests Bitcoin season. The index is a useful descriptive tool, but it is not a prediction or a buy signal. Use it alongside other data and always consider the risks.
Disclaimer: This article is for information only and is not investment, financial or trading advice. Cryptocurrency prices are highly volatile. Always do your own research.
