Every cycle, the same question floods crypto group chats: "Is it altcoin season yet?" Altcoin season is the phase when most altcoins outperform Bitcoin at the same time — when capital rotates out of BTC and lifts the broader market faster than it lifts Bitcoin itself. The problem is that "most alts are pumping" is a feeling, not a measurement. The Altcoin Season Index turns that feeling into a single objective number by answering one precise question: over the last 90 days, what share of the top altcoins have actually beaten Bitcoin? As of today the index reads 62/100 — the Neutral zone. Fifty-seven of the 92 qualifying altcoins have outperformed BTC over the window, but that is short of the supermajority that defines a true altcoin season. This guide breaks down exactly what the number measures, how it is built, and the honest limits of compressing an entire market into one statistic.
What Is the Altcoin Season Index?
The Altcoin Season Index is a breadth indicator. Where a price chart tracks how much something moved, a breadth indicator tracks how many things moved together. Specifically, this index measures what percentage of the top 100 cryptocurrencies have outperformed Bitcoin over a rolling 90-day window, then expresses that share as a number from 0 to 100.
The logic is deliberately simple. If 90 of the top altcoins have beaten Bitcoin over the past quarter, the index reads near 90 and the market is overwhelmingly favoring alts — a textbook altcoin season. If only 10 have beaten BTC, the index reads near 10, and Bitcoin is the clear leader. The reading is not a price and not a sentiment poll; it is a head-count of winners and losers measured against a single benchmark, Bitcoin.
By convention, a reading of 75 or above is what qualifies as "Altcoin Season" — at least three-quarters of the field beating Bitcoin. A reading of 25 or below is "Bitcoin Season," where Bitcoin is outperforming the overwhelming majority of alts. Everything in between is a neutral or transitional zone. The threshold is intentionally high: genuine altcoin seasons are rare events, and the 75 line exists to keep the label meaningful rather than triggering on every two-week alt bounce.
How the Altcoin Season Index Is Calculated
The calculation is a five-step head-count, and understanding each step is what separates reading the number from trusting it blindly.
First, take the top 100 cryptocurrencies ranked by market capitalization. Using the top 100 is a deliberate choice — it captures the assets that actually hold meaningful capital, while ignoring the long tail of micro-caps whose 90-day returns are dominated by noise and illiquidity. The composition is re-pulled on every refresh, so the list always reflects the current top of the market.
Second, remove the assets that would distort the reading. Bitcoin itself is excluded because it is the benchmark, not a competitor. Stablecoins are excluded because a dollar-pegged token returning roughly 0% is not a meaningful "altcoin" data point — it would simply count as an automatic loser to BTC in any up market and an automatic winner in any down market. Wrapped and liquid-staked tokens (wrapped BTC, staked ETH derivatives, and similar) are also removed, because they mechanically track an underlying asset already represented in the set. After these exclusions, roughly 90 genuine altcoins remain — today the count is 92.
Third, compute the 90-day percentage return for Bitcoin and for each remaining altcoin, using the price 90 days ago versus the price today. Fourth, count how many of those altcoins delivered a higher 90-day return than Bitcoin. Fifth, divide that count by the number of valid altcoins and multiply by 100. That percentage is the index. Today: 57 of 92 alts beat Bitcoin's 90-day return of −6.9%, which rounds to 62.
Why 90 days and not 30 or 7? The window length is the single most important design decision. A 7-day window would flip between "altcoin season" and "Bitcoin season" on every weekly candle, making it useless for cycle positioning. Ninety days is long enough to filter out short-lived relief rallies and single-narrative pumps, but short enough to still capture a genuine regime change within a quarter. It measures sustained outperformance, not a flash in the pan.
How to Read the Index
The 0-100 scale maps to three regimes. The boundaries are conventions rather than hard mathematical breaks — a reading of 74 behaves almost identically to 76 — but the zones describe genuinely different market structures.
| Zone | Range | What It Means |
|---|---|---|
| Bitcoin Season | 0 – 25 | A quarter or fewer of top alts are beating BTC. Capital is concentrated in Bitcoin — typically early-cycle accumulation or a risk-off flight to the most liquid asset. Most altcoins are bleeding against BTC even if their dollar price is flat. |
| Neutral / Transition | 26 – 74 | A mixed field. Some alts outperform, some lag — no broad rotation in either direction. This is where the market spends most of its time. Trend within the band matters more than the absolute level. |
| Altcoin Season | 75 – 100 | Three-quarters or more of top alts are beating Bitcoin. Capital is rotating broadly out of BTC into the rest of the market. Historically rare, often euphoric, and rarely sustained for long. |
The most common mistake is treating the index as a buy/sell switch that flips at 75. It is not. A reading of 62 today does not mean "almost altcoin season, get ready" any more than a reading of 40 means "Bitcoin season is coming." Breadth indicators are about regime, not timing.
The reading skill that matters is direction of travel, not the absolute level. An index at 60 that has climbed from 35 over three weeks tells a very different story — broadening alt strength — than an index at 60 that has fallen from 85, which signals a fading altcoin season as money rotates back toward Bitcoin. The number tells you where breadth is; the trajectory tells you where it is heading. Always read the chart, not just the headline figure.
It is also worth remembering what a high reading does and does not promise. An index of 80 means 80% of top alts beat Bitcoin — it says nothing about whether they beat the dollar. In a sharp market-wide downturn, alts can fall less than Bitcoin and still register a high "altcoin season" reading while every position is underwater in USD terms. Breadth versus BTC is not the same thing as profit.
Historical Context: How Rare Altcoin Seasons Actually Are
The defining feature of altcoin seasons is how infrequent and short-lived they are. Across the past two crypto cycles, sustained periods where the overwhelming majority of large alts beat Bitcoin can be counted on one hand — and each lasted weeks to a couple of months, not the perpetual "alt summer" that retail memory tends to imagine.
The clearest example was the 2017-into-early-2018 era. The ICO boom flooded capital into Ethereum and a wave of new tokens, and Bitcoin Dominance collapsed from around 95% toward the low 40s and briefly under 40% in early 2018. With dominance cratering, the breadth of alts beating BTC was near its structural maximum — the deepest, broadest altcoin season on record. It ended exactly as these episodes always do: abruptly, with the 2018 bear market unwinding alts far faster than Bitcoin.
The 2021 cycle produced two distinct bursts rather than one continuous run: a spring 2021 surge as Bitcoin Dominance fell sharply, and a second leg later that year. Both saw the majority of large-cap alts outperform Bitcoin for a stretch of weeks before reversing. The pattern across both cycles is consistent — altcoin seasons arrive late in a broader uptrend, run hot for a relatively short window, and give back the relative gains quickly once Bitcoin reasserts dominance.
There is an important honest caveat about historical readings of this specific index. A faithful 90-day, top-100 breadth figure can only be reconstructed for as far back as clean daily price history exists for the assets that were in the top 100 at the time — and the composition of that top 100 changes constantly. Precise historical index values for, say, a given week in 2017 are therefore not directly comparable to today's reading. What is verifiable and reliable is the market behavior: dominance collapses, broad alt outperformance, then a sharp reversal. Treat the cycle pattern as the lesson, not a single back-dated number.
Today at 62 (Neutral): the index sits in the upper half of the neutral band — more alts are beating Bitcoin than not, but well short of the 75 threshold that defines a true altcoin season. This is a market leaning toward alts without a confirmed broad rotation. As always, the trend over the coming weeks carries more information than this single reading.
How Traders Actually Use the Index
The Altcoin Season Index is a confirmation tool, not a trigger. On its own it tells you the current breadth regime; its real value emerges when it is cross-referenced against the indicators that measure the same rotation from a different angle. None of the following is financial advice — it is how the indicator is commonly read.
Confirm rotation with Bitcoin Dominance
The Altcoin Season Index and Bitcoin Dominance are two views of the same phenomenon. Dominance measures the share of total market cap held by Bitcoin; the Altcoin Season Index measures how many alts are beating Bitcoin. They are inversely related almost by construction — when capital genuinely rotates into alts, dominance falls and the season index rises together. The high-confidence signal is alignment: a rising Altcoin Season Index AND falling Bitcoin Dominance, ideally with total market cap rising. When those move together, the rotation is corroborated rather than guessed. When they diverge — the index rising while dominance also rises — the move is usually noise or a narrow, single-narrative pump.
Layer in sentiment with Fear & Greed
Breadth tells you what capital is doing; the Fear & Greed Index tells you how participants feel about it. A climbing Altcoin Season Index alongside extreme greed often marks the euphoric late stage of a rotation — the point where chasing has the worst risk/reward. A rising season index emerging out of a fearful, beaten-down market is a very different, earlier-stage signal. Reading breadth and sentiment together is far more informative than either alone.
Watch the threshold cross as context, not a command
Some traders treat the 75 line as a regime flag: above it, the playbook tilts toward holding or rotating into alts; below it, toward Bitcoin-weighted positioning. Used this way the index is a coarse portfolio-weighting input, not an entry signal for any specific token. The crossing tells you the macro tide has turned; it never tells you which boat to be in.
What it cannot tell you
The index does not tell you which altcoin to buy, when to enter or exit a specific position, how long the current breadth regime will last, or whether high breadth versus Bitcoin will translate into dollar profit. It is a single macro gauge. Treat it as one input among several, never as instruction.
Limitations and Honest Caveats
- Backward-looking by construction — the index measures the trailing 90 days. By the time it crosses into Altcoin Season territory, much of the rotation it describes has already happened. It confirms a regime more than it forecasts one
- Seasons can end abruptly — breadth can collapse far faster than it built. A reading of 80 can fall back through neutral in a matter of weeks when Bitcoin reasserts dominance, leaving late entrants exposed
- Sensitive to the top-100 composition — the reading depends on which assets are in the top 100 at calculation time. As coins enter and exit the rankings, the denominator shifts, and a few large movers can swing the percentage
- Breadth is not profit — a high reading means most alts beat Bitcoin, not that they rose in dollar terms. In a market-wide drawdown, alts can outperform BTC while everything still loses value
- Says nothing about WHICH alt — the index is a head-count, not a stock-picker. It tells you the field is broadly winning, never which specific token will
- Quarterly resolution — a 90-day window is intentionally slow. It is built for cycle positioning, not for timing short-term swings, and will always lag fast reversals
Related Rotation and Sentiment Indicators
The Altcoin Season Index is one face of a small family of indicators that, read together, describe crypto market rotation from complementary angles. Each fills a gap the others leave open — breadth, share, capital parked on the sidelines, and the leading-edge rotation into Ethereum.
- Bitcoin Dominance — the mirror image of this index. The season index counts how many alts beat BTC; dominance measures the capital share BTC holds. They are two sides of the same rotation, and reading them together is the highest-confidence confirmation either one offers
- Fear & Greed Index — the sentiment overlay. Tells you whether a given breadth reading is happening in fear or euphoria, which completely changes what it implies for risk
- ETH/BTC Ratio — the leading edge of rotation. Capital classically flows from Bitcoin into Ethereum first, then out into the broader alt market. A rising ETH/BTC ratio often front-runs a rising Altcoin Season Index
- Stablecoin Dominance — measures dry powder. Falling stablecoin dominance during a rising season index means parked capital is actively deploying into alts — fuel for the rotation
Continue reading: Bitcoin Dominance
Altcoin Season and Bitcoin Dominance are the same rotation viewed from opposite ends. When dominance falls AND this index climbs, the rotation is confirmed — see how the BTC.D chart works.
Continue reading: Fear & Greed Index
Breadth tells you what capital is doing; sentiment tells you how it feels. A rising Altcoin Season Index reads very differently in greed than in fear — read the sentiment guide.
Track the Live Altcoin Season Index
See the current reading, the 90-day history chart, today / yesterday / last-week / last-month comparisons, and the top alts currently outperforming Bitcoin.
Frequently Asked Questions
What is a good altcoin season index reading?
There is no single "good" number — it depends on what you hold. A reading of 75 or above signals a true altcoin season, where at least three-quarters of top alts are beating Bitcoin; an alt-heavy portfolio benefits most in that regime. A reading of 25 or below signals Bitcoin Season, which favors BTC-weighted positioning. The neutral 26-74 band, where the index reads 62 today, is a mixed market with no broad rotation. More important than the absolute level is the direction of travel over recent weeks.
When was the last altcoin season?
The two clearest examples in recent crypto history were the 2017-into-early-2018 ICO-driven run and the two bursts of the 2021 cycle, when Bitcoin Dominance fell sharply and the majority of large-cap alts outperformed Bitcoin for a stretch of weeks. The consistent lesson is that altcoin seasons are rare, arrive late in a broader uptrend, and reverse quickly. As of today the index reads 62 (Neutral) — leaning toward alts but short of a confirmed season.
How is altcoin season different from bitcoin dominance?
They measure the same rotation from opposite directions. Bitcoin Dominance is the share of total crypto market capitalization held by Bitcoin. The Altcoin Season Index is a head-count: the percentage of top altcoins that have beaten Bitcoin over 90 days. When capital rotates into alts, dominance falls and the season index rises together — which is why traders read the two side by side. Dominance is a capital-weighted share; the season index is a breadth count where every alt gets one vote regardless of size.
Does altcoin season mean all altcoins go up?
No. The index measures how many alts beat Bitcoin, not whether they rose in dollar terms. In a market-wide downturn, most alts can fall less than Bitcoin and still register a high "altcoin season" reading while every position is underwater in USD. It is also a head-count of the top 100, so it can be high even when the long tail of smaller alts is lagging. A high reading describes broad relative strength against BTC — not a guarantee that any specific token is profitable.
How long does altcoin season last?
Historically, weeks to a couple of months — rarely longer. Because the index uses a trailing 90-day window, a true season also fades gradually in the reading even after the underlying rotation has stopped, since older outperformance stays in the calculation until it rolls off. The practical takeaway is that altcoin seasons are short and tend to end abruptly when Bitcoin reasserts dominance, so the regime is far more fragile than its reputation suggests.
How often does the Altcoin Season Index update?
The live reading on AltcoinSignal recomputes every hour. A background job re-pulls the 90-day performance of the current top 100 coins, excludes Bitcoin plus stablecoins and wrapped or staked tokens, recounts how many of the remaining alts beat Bitcoin, and snapshots the result into a history table. That history drives the today / yesterday / last-week / last-month comparisons and the 90-day chart on the live tool page.