Altcoin Season Index Explained: When Do Alts Actually Outperform Bitcoin?

How it's calculated

Alphabit's Altcoin Season Indexstarts from the top 50 coins by market cap, strips out stablecoins, wrapped/staked duplicates, and tokenized treasuries — none of those are altcoin bets in the sense the index is trying to measure — then computes each remaining coin's trailing 90-day return against Bitcoin's over the same window. The index itself is simply the percentage of that set that beat Bitcoin.

A handful of top-50 coins get skipped in any given run — ones without a matching listing on the price source used, or without enough trading history yet — and the index is computed over whatever set remains scoreable, disclosed on the page itself rather than silently ignored.

How it's historically been read

A reading of 75 or above — three-quarters of the top 50 beating Bitcoin over three months — has conventionally been called altcoin season: capital broadly rotating out of Bitcoin and into smaller-cap alternatives chasing higher beta, typically a later-cycle, higher-risk-appetite phase.

A reading of 25 or below is Bitcoin season— capital concentrating in Bitcoin specifically, which has historically shown up both early in a bull cycle (Bitcoin leads, alts lag) and during risk-off periods (Bitcoin is treated as the relatively safer crypto asset in a drawdown). The same reading can mean two different things depending on the broader trend, which is why it's read alongside price direction, not in isolation.

Limitations

The 75/25 thresholds are a convention borrowed from common industry usage, not a statistically derived boundary — treat a reading of 72 and a reading of 78 as more similar than the "no clear season" vs. "altcoin season" labels might suggest. The index is also a snapshot of the specific 50 coins large enough to qualify today; survivorship and reshuffling in and out of the top 50 over time mean long-run historical comparisons should be read with some caution. It's context for allocation, not a timing signal — see Bitcoin Dominance for the closely related market-cap-share view of the same rotation.

Frequently asked questions

What is the Altcoin Season Index?

It tracks what share of the top 50 coins by market cap have beaten Bitcoin's return over the trailing 90 days, with stablecoins, wrapped and staked duplicates and tokenized assets excluded. The result is a 0-100 reading of how broadly capital is rotating out of Bitcoin and into altcoins.

What number counts as altcoin season?

A reading of 75 or above is conventionally called altcoin season — three-quarters of the qualifying top 50 have outperformed Bitcoin over the trailing 90 days. A reading of 25 or below is Bitcoin season, with capital concentrating in Bitcoin instead.

Are the 75 and 25 thresholds statistically derived?

No. They are a convention borrowed from common industry usage, not a boundary derived from data. A reading of 72 and a reading of 78 are more similar to each other than the 'no clear season' and 'altcoin season' labels suggest.

What is the difference between the Altcoin Season Index and Bitcoin Dominance?

They describe the same rotation from two angles. The Altcoin Season Index counts how many coins outperformed Bitcoin, so it is a breadth measure. Bitcoin Dominance measures Bitcoin's share of total crypto market cap, so it is weighted by size — a single large altcoin can move dominance without moving breadth.

Can the Altcoin Season Index be used to time trades?

It is context for allocation rather than a timing signal. The index also reflects the specific 50 coins large enough to qualify today, so survivorship and reshuffling in and out of the top 50 mean long-run historical comparisons should be read with caution.