What Is the Altcoin Season Index and How to Use It

Every crypto cycle has a moment where Bitcoin stops being the only game in town. Suddenly, smaller coins start outperforming it — Ethereum surges, Solana doubles, and even tokens you've never heard of are printing triple digits. That's altcoin season. And there's a single number that tells you exactly how deep into it the market is: the altcoin season index. Understanding what it measures and how to act on it is one of the most underrated edges a crypto trader can have.

What Is the Altcoin Season Index?

The altcoin season index is a numerical indicator that measures how many of the top 100 cryptocurrencies (by market cap, excluding stablecoins and wrapped tokens) have outperformed Bitcoin over the last 90 days. It was popularized by CoinMarketCap and gives you a clean, objective snapshot of whether the market is in Bitcoin season, altcoin season, or somewhere in between.

Think of it like a sports league standings board. Bitcoin is always on the board. But when most of the other 99 players are outscoring it — that's when the crowd goes wild for altcoins. The index captures that shift in a single number from 1 to 100.

Key Takeaway: The altcoin season index tells you what percentage of the top 100 altcoins are beating Bitcoin over 90 days. Higher score = more altcoins winning = stronger altcoin season.

Here's the simple breakdown of what the number means in practice. A score below 25 means you're firmly in Bitcoin season — BTC is crushing everything else, and most altcoins are either flat or bleeding against it. A score above 75 means altcoin season is in full swing — the majority of the market is outrunning Bitcoin and traders are rotating aggressively into smaller cap assets. The range between 25 and 75 is the gray zone where the market hasn't clearly committed to either direction.

How the CMC Altcoin Season Index Is Calculated

The CMC altcoin season index — published by CoinMarketCap — uses a straightforward methodology. It looks at the top 100 cryptocurrencies by market capitalization (after excluding stablecoins like USDT and USDC, and wrapped tokens like WBTC that track Bitcoin's price anyway). For each of those coins, it checks whether that coin's 90-day percentage return is higher than Bitcoin's 90-day percentage return. If 75 or more of those coins beat Bitcoin over that window, the index registers altcoin season.

The 90-day window is deliberate. Short-term spikes are meaningless — they happen all the time and reverse just as fast. A 90-day window filters out the noise and captures actual momentum shifts. When most of the market sustains outperformance against Bitcoin for three months, that's a structural rotation, not a random day's price action.

• Takes the top 100 cryptos by market cap
• Excludes stablecoins and wrapped tokens (they don't reflect real market behavior)
• Compares each coin's 90-day return against Bitcoin's 90-day return
• Counts how many coins outperformed BTC
• Expresses that count as a percentage — that's the index score

One thing worth knowing: the composition of the top 100 changes over time. Coins that drop out get replaced by newer entrants. This means the index is always measuring the current market structure, not a fixed basket. It's a live pulse on where money is flowing, not a historical artifact.

Key Takeaway: CMC's methodology is transparent and simple — no black box. 75+ out of 100 altcoins beating Bitcoin over 90 days = altcoin season. You can verify it yourself on CoinMarketCap's altcoin season index page.

How to Check What the Altcoin Season Index Is Right Now

Checking the altcoin season index right now takes about 10 seconds. CoinMarketCap publishes it in real time on their main site under the 'Tools' section. It updates daily and shows you both the current score and a chart of how it's trended over time — which is often more useful than the number alone. A score climbing from 40 to 65 over two weeks tells a different story than a score that's been stuck at 65 for three months.

Beyond CoinMarketCap, several other resources track similar data. Blockchaincenter.net has its own altcoin season chart with longer historical data going back multiple market cycles. Platforms like VoiceOfChain aggregate real-time trading signals and market phase indicators — so instead of checking the index manually every day, you can get context-aware alerts when conditions shift between Bitcoin and altcoin season. That's especially valuable when you're managing multiple positions across exchanges like Binance or Bybit and don't want to miss a rotation.

The index alone is just one data point. Smart traders cross-reference it with Bitcoin dominance (BTC.D on TradingView), total crypto market cap excluding Bitcoin (TOTAL2), and volume flows. When the altcoin season index is rising while BTC dominance is falling and TOTAL2 is breaking upward — that confluence is a much stronger signal than any one metric alone.

Key Takeaway: Don't just check the score — watch the trend. An index moving from 30 to 60 is a trade setup. An index stuck at 60 for months might be topping out.

What Altcoin Season Actually Does to Your Portfolio

During altcoin season, the dynamics of crypto portfolios change dramatically. Bitcoin might still be going up — but altcoins are going up faster. That means a Bitcoin-heavy portfolio underperforms a diversified altcoin portfolio even in a rising market. The opportunity cost of holding only BTC during peak altcoin season can be enormous.

Here's a concrete example: In the 2021 altcoin season, Bitcoin went from roughly $30,000 to $65,000 — more than doubling. Meanwhile, Ethereum went from $1,800 to $4,400 (2.4x), Solana went from $25 to $250 (10x), and countless smaller caps did 5x to 50x in the same window. A pure Bitcoin holder did well. An altcoin season trader did significantly better.

The flip side is just as real. During Bitcoin season, altcoins often bleed against BTC even when they're nominally going up in USD terms. You might hold an altcoin that gains 20% in dollar value while Bitcoin gains 60% — meaning in BTC terms, you lost ground. This is why the index matters: it helps you know which side of this dynamic you're currently on.

• Altcoin season: rotate a portion of BTC holdings into quality altcoins to capture higher beta
• Bitcoin season: reduce altcoin exposure, hold BTC or stablecoins to preserve capital
• Gray zone (25–75): maintain a balanced portfolio, watch for directional confirmation
• Always keep enough BTC or stablecoin to survive a sudden reversal

Using the Altcoin Season Index in Your Trading Strategy

The index works best as a macro filter — it tells you the environment you're trading in, not exactly what to buy. Think of it like checking the weather before you dress. A score above 75 doesn't mean every altcoin is a buy. It means the wind is at your back if you're long on quality projects. A score below 25 means you're likely fighting the current.

One practical approach: use the index as a portfolio allocation guide. When the index is below 30 and trending down, keep 70–80% of your crypto portfolio in Bitcoin. As it climbs above 50 and holds, gradually shift 30–50% into large-cap altcoins like ETH, SOL, or BNB. If it pushes above 75 with strong volume backing, you can take more targeted positions in mid and small caps — the coins that actually deliver the outsized returns during altcoin season.

On Binance and OKX, you can easily compare your altcoin positions against a BTC pair to gauge whether you're actually outperforming. If you're long ETH and ETH/BTC is falling while the altcoin season index is 80, something specific is wrong with that position — either take profits or reassess. Platforms like Bybit also offer useful portfolio tracking tools that show your holdings denominated in BTC, making this comparison straightforward.

Another edge: use the index to time entries and exits, not just allocations. When the index crosses above 75 for the first time in a cycle, that's often the early phase of a run — not the end. But when it's been above 75 for weeks and starts falling back below 60, that rotation is cooling. Late-cycle altcoin season is where most retail traders get burned chasing pumps that are already ending. Services like VoiceOfChain can help here by sending real-time signals when market conditions shift, so you're not relying on checking charts manually every hour.

Key Takeaway: The altcoin season index is a macro filter, not a buy signal. Use it to set your allocation bias, then pick your assets carefully within that context. High index + strong fundamentals = favorable setup. High index + random hype coin = still a gamble.

For traders on exchanges like KuCoin or Gate.io where the altcoin selection is massive, the index is especially useful as a filter. When altcoin season is confirmed, the rising tide lifts many boats — but you still want to focus on coins with real volume, verified liquidity, and a clear narrative. The index tells you the season is here; your own research determines which crops to harvest.

Frequently Asked Questions

Conclusion

The altcoin season index strips away the noise of daily price action and shows you the actual rotation happening in the market. It won't tell you which coin to buy or when the exact top is in — but it gives you an honest answer to the most important question in crypto positioning: is the market rewarding risk right now, or punishing it? When most of the top 100 are beating Bitcoin, that's your environment signal. Trade accordingly, stay alert for reversals, and use platforms like VoiceOfChain to catch shifts in real time rather than reading about them after the move is done.