Should You Own Altcoins, or Just Bitcoin? What the Dominance Data Shows
5 min read
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5 min read
If you put money into altcoins at the start of 2026 expecting them to outrun Bitcoin, the data says you would likely be behind right now. Ethereum is down about 62% from its own 2025 peak. Bitcoin is down about 49% from its own peak over the same stretch. Same crash, different depth, and the gap between those two numbers has a name: Bitcoin dominance.
Bitcoin dominance is simply Bitcoin's share of the total value of all cryptocurrencies combined. When it rises, altcoins as a group are losing ground to Bitcoin. When it falls, altcoins are gaining on it. Whether owning altcoins on top of Bitcoin has actually paid off depends almost entirely on which direction that number was moving at the time, not on a fixed rule.
Divide Bitcoin's market capitalization by the market capitalization of every cryptocurrency added together, and you get Bitcoin dominance, usually written as a percentage. As of early August 2026, Bitcoin's market cap sits around $1.3 trillion against a total crypto market of roughly $2.2 to $2.3 trillion, putting dominance at about 58% to 59% (CoinMarketCap, CoinGecko, both retrieved 2026-08-06).
That is not a static number. It has swung from above 60% in April 2026, to roughly 63% in June, a four-year high, before pulling back to the high 50s in the weeks since (BeInCrypto, retrieved 2026-08-06). A related measure, the Altcoin Season Index, tracks how many of the top 50 or so altcoins are outperforming Bitcoin over a rolling 90-day window. It needs a reading of 75 or higher to count as a genuine "altcoin season." As of the most recent readings this year it has sat around 35 to 37, firmly in what the index calls Bitcoin Season (CoinMarketCap Academy, retrieved 2026-08-06).
To see why this ratio matters, look at what happened the last time it moved sharply in the other direction. Bitcoin dominance opened 2021 at about 69.5% and fell to roughly 38% to 39% by the second half of the year (various dominance trackers cross-referenced against CoinGecko's historical chart, retrieved 2026-08-06). Over that same window, Ethereum ran from about $730 to a peak near $4,300, and Solana went from about $1.50 to around $50. The Altcoin Season Index hit 98 out of 100 on April 16, 2021, essentially a confirmed altcoin season.
That was a period where owning altcoins alongside Bitcoin, or instead of it, would have meaningfully outperformed holding Bitcoin alone. It is also the period most people picture when they think about what crypto diversification can do. It is not the period the market has been in for most of 2026.
Dominance spent roughly eight months, August 2025 through April 2026, moving sideways before breaking above 60% (BeInCrypto, retrieved 2026-08-06). The clearest way to see what that meant in practice is to compare how far Bitcoin and Ethereum have each fallen from their own separate 2025 highs.
| Asset | 2025 peak | Price now (Aug 6, 2026) | Decline from peak |
|---|---|---|---|
| Bitcoin | ~$126,198 (Oct 6, 2025) | ~$64,580 | ~49% |
| Ethereum | ~$4,950 (Aug 25, 2025) | ~$1,890 | ~62% |
(Bitcoin figures from CoinDesk and Bitbo; Ethereum peak from AiCoin and Axios; Ethereum current price from CoinDesk. All retrieved 2026-08-06. Declines are self-derived from the two sourced prices in each row.)
Both assets crashed. Ethereum crashed harder. That gap, roughly 13 percentage points of extra decline, is dominance rising made visible in two real prices instead of an abstract ratio.
The honest answer is that dominance data does not hand you a permanent yes or no. It hands you a read on the current regime:
Neither state is permanent, and the transition between them has not historically announced itself in advance. The Altcoin Season Index existing as a tracked, published number is itself evidence that professional traders treat this as a regime to monitor continuously, not a decision to make once.
The number that matters for your own portfolio is not the market-wide dominance figure, it is how your specific mix of Bitcoin and altcoins has actually performed against Bitcoin alone over the period you have held it. NetWort's Holdings page breaks down each position's return individually, so you can see directly whether your altcoin sleeve has helped or hurt versus simply holding Bitcoin or Ethereum on their own. If you are weighing how big that sleeve should be in the first place, the crypto allocation percentage breakdown and the bitcoin halving price history piece are both useful next reads.