Altcoin Season Index

The Altcoin Season Index measures how many of the largest cryptocurrencies have beaten Bitcoin over the past 90 days. Here it covers the top 50 coins by CoinGecko data and updates once a day. A high reading means outperformance against BTC is spread across many altcoins. A low reading means Bitcoin has outrun most of them. “Altcoin season,” or altseason, is the term for a stretch when altcoins as a group outperform Bitcoin. “Bitcoin season” is the reverse.

How the value is calculated

Each coin in the top 50 gets one test: was its 90-day return higher than Bitcoin’s 90-day return over the same window? The index is the share of coins that pass, on a 0 to 100 scale:

Index = (coins outperforming BTC over 90 days ÷ 50) × 100

Hypothetical example: if 30 of the 50 coins beat Bitcoin’s 90-day return, the index reads 60. If only 10 do, it reads 20. Each coin is worth 2 points. A single coin crossing above or below Bitcoin’s return moves the reading by 2. This is why the daily value can step up or down by several points even when the market looks calm.

The vs BTC column in the coin table shows a coin’s 90-day return minus Bitcoin’s 90-day return, in percentage points. Any positive figure counts as “Yes” in the outperformance column, whether the margin is 1 point or 200. You can recover Bitcoin’s own 90-day return from any row by subtracting the “vs BTC” figure from the coin’s return.

Reading the gauge and chart

The gauge places the current value in one of three zones: Bitcoin season, Neutral or Altcoin season. The 30-day average smooths out the day-to-day flips described above, so it gives a steadier read of direction than a single day’s number. The chart plots the index against Bitcoin’s price on a log scale. You can see whether broad altcoin outperformance tends to arrive while BTC is rising, falling or moving sideways.

The all-time high, all-time low and 1-year average start in February 2026. They describe the range of that period, not of earlier crypto cycles.

What drives the reading

Bitcoin’s 90-day return sets the hurdle every coin must clear. When BTC rallies hard, fewer altcoins keep pace and the index falls. When BTC stalls, coins with their own catalysts (protocol upgrades, token unlocks, sector narratives) can clear the bar more easily. The index compares relative returns only. A coin that fell 10% while Bitcoin fell 20% counts as outperforming. A high reading during a broad decline means altcoins lost less, not that they gained.

Limits

• Breadth, not size. Every coin counts equally, whatever its margin over BTC, and small coins weigh the same as large ones.
• Moving membership. The top 50 changes as market caps shift, so the basket being measured is not fixed.
• Lag. A 90-day window describes what has already happened. It reacts slowly to turns and says nothing on its own about the next 90 days.

The index is different from Bitcoin dominance, which tracks BTC’s share of total crypto market capitalization. Dominance is weighted by size. This index counts how many coins are winning.