BTC and ETH move together, except when they don't
Two lines on a chart, both starting at zero, both climbing and dropping over the same 12 hours. When they trace each other almost exactly, you're looking at the crypto market doing its usual thing. When they peel apart, something specific to one asset has happened and it's worth knowing what. That's the entire information content of a normalised BTC-versus-ETH chart — and it's most of what anyone actually needs to read crypto price action without a trading terminal.
Here's the live version. The last 12 hours of BTC (gold) and ETH (cyan), both rebased to 0% at the start of the window. The spread between the lines at any moment tells you how much one coin is out- or under-performing the other, relative to where they both started:
The rest of this piece is about how to read that chart without overthinking it, why BTC and ETH are so tightly correlated most of the time, what it means when they separate, and a handful of related questions worth a paragraph each at the end. None of it is trading advice. It's literacy for looking at crypto charts without being manipulated by the visual tricks most sites use.
What "normalised to zero" actually means
If you plot BTC and ETH's raw prices on the same chart, you get nothing useful. BTC trades somewhere in the five-figure dollars, ETH in the three or four figures. ETH's entire daily swing might be smaller in dollar terms than a BTC wick, even on a day where ETH moves proportionally far more. The absolute-dollar chart hides the information.
Rebasing to zero fixes this. You pick a starting point — here, 12 hours ago — and compute every subsequent price as a percentage change from that starting price. BTC at $78,000 going to $78,780 shows as +1.0%. ETH at $3,200 going to $3,264 also shows as +1.0%. On the chart, both those moves are the same visual size. That's the point: they become comparable. You can now answer "is ETH outperforming BTC today?" with a glance instead of a calculation.
Professional traders call this "rebasing" or "indexing". Charting platforms sometimes call it "relative performance" view. Whatever the label, the math is one subtraction and one division per sample. Cheap, honest, useful.
Once you're looking at the rebased chart, the BTC line and the ETH line become directly comparable. Higher line = outperforming. Steeper slope = moving faster. Crossover point = the moment one overtook the other. Spread at the right edge = current outperformance delta. That's all the basic reading you need.
Why BTC and ETH usually move together
If you watch the chart above for any stretch of normal market hours, you'll see the two lines trace each other surprisingly closely. Multiple academic studies place the BTC-ETH price correlation over rolling 30-day windows somewhere between 0.7 and 0.95, depending on the period measured. Informal terminology: "crypto moves as one asset most of the time."
Three reasons:
Shared liquidity providers. The same market-making firms (Jane Street, Wintermute, GSR, Cumberland, and a handful of others) quote both BTC/USDT and ETH/USDT on the same exchanges. When their risk models see aggregate crypto risk moving, they adjust quotes on both pairs at the same time. This produces tight, fast correlation on a minute-by-minute basis that wouldn't exist if the two markets were operated by different desks.
Shared macro drivers. Crypto as an asset class correlates (loosely, with debates) with other risk assets — tech stocks, high-yield credit, speculation-heavy segments of the market. A risk-off news event (rate-hike surprise, bank failure, geopolitical flashpoint) pulls both BTC and ETH down together. A risk-on event (rate cut, ETF approval, regulatory thaw) pulls both up. Neither asset has a meaningful fundamental story that trades independently of the other on a daily basis.
Shared speculators. Retail and prop-desk traders typically run crypto portfolios, not single-coin positions. When they de-risk they sell both. When they re-risk they buy both. The dollar amounts differ, but the direction is usually the same on the same day. BTC also sets the rhythm at a price-structure level — BTC's gravitational levels (round numbers, recent extremes) tend to anchor the wider crypto market's attention even when ETH has its own catalyst.
Together these three keep the two lines on the rebased chart mostly within a percent or so of each other for most of any given 12-hour window.
When they diverge
The interesting moments are when they don't. Most divergence falls into three buckets:
Idiosyncratic news for one coin. An exchange announces listing a particular altcoin, and ETH outperforms because that altcoin trades in ETH pairs. A regulator singles out one asset in a statement — in practice this has happened more often to ETH than BTC because of the "is it a security" history. A protocol upgrade ships (the Ethereum Merge, Dencun, Prague) and ETH reacts to its own calendar. In all of these, BTC continues to drift with macro while ETH jumps to its own drum for a few hours.
Rotation. Risk-on periods often see capital flow from BTC (the "safer" crypto) into ETH and further into higher-beta altcoins. The normalised chart captures the first leg of this rotation cleanly — ETH's line lifts above BTC's line and stays there for hours or days. The classic "altseason" begins with this exact signature on a BTC-ETH normalised chart.
Liquidity shocks. An outage at a major exchange, a cascade of liquidations in BTC-margined positions, a stuck funding-rate spike — these can create short bursts where one asset's price wobbles while the other stays steady. Usually resolves within a few hours. On a normalised chart it looks like a sharp vertical separation that closes itself. Divergences also tend to widen during the London session opens, when European desks process overnight news and one asset gets the headline before the other.
The peak-divergence line on the live chart above marks the largest |ETH% − BTC%| gap in the visible window. On quiet days that peak is well under a percent. On interesting days it can be several.
Reading the chart, in order
- Overall shape. Both lines up = broad risk-on day. Both down = broad risk-off. One up, one down = something specific. A flat-line on both for hours = nothing happening, which is most of the time.
- Ending delta. The two labelled percentages on the right show where the lines are now. The bigger the gap, the stronger the relative-performance story.
- Where they crossed. If the lines crossed at any point in the window, that's the moment outperformance flipped. Often correlates with a specific tick-level event worth looking up.
- Peak divergence. Already marked on the chart. Tells you the widest gap that occurred during the window, regardless of where the lines ended. A big peak that closed back up means volatility without lasting impact — a pattern worth recognising.
That's a four-step reading of any normalised dual-line crypto chart. Applies to BTC-ETH, BTC-SOL, ETH-SOL, or any other comparable pair.
How long does divergence last
A useful related question: when the two lines separate, how long before they come back together? The answer is "it depends on what caused the separation," but some rough patterns hold across enough cycles to be worth knowing.
Liquidity-shock divergences close fastest. A panicked cascade that moves one coin 2% while the other stays put usually reverses within one to four hours — market makers refill the thin side, arbitrageurs pull the prices back into line, and the chart looks normal again by the next session handoff. These are often invisible unless you're watching minute-by-minute.
News-driven divergences last a session or two. An unexpected regulatory statement, a protocol-specific announcement, or a listing on a major venue typically holds a 2-4% BTC-ETH spread for six to twelve hours before the broader market digests it and correlation reasserts. If the chart still shows the divergence the next morning, the news was bigger than it looked.
Rotation divergences persist for days or weeks. The classic ETH-outperforms-BTC pattern that precedes altseason isn't something you see on a 12-hour chart — it's the kind of thing that reveals itself when you compare today's normalised chart to last week's and see ETH has been steadily above BTC the entire time. When that's happening, the individual 12-hour snapshots become less interesting and the multi-day trend is the real signal.
Why this matters for altcoin-watchers
The normalised BTC-ETH chart is the first reading most analysts run when they're trying to call the "altseason" direction — the general thesis being that capital flows down the risk curve from BTC into ETH first, then into large-cap alts, then into the long tail. If BTC-ETH is flat and tight, altcoins tend to be in a quiet consolidation. If ETH has been outperforming BTC for days, alts usually follow within weeks. If ETH is underperforming BTC, the "BTC dominance" narrative is back and alts tend to chop sideways while BTC runs.
This isn't a prediction mechanism — plenty of counterexamples exist. But as a framing tool for "what's the current regime", the rebased chart carries most of the signal a casual observer needs.
A small plug for calmer charts elsewhere
Most crypto websites add urgency to this exact same information: blinking price tickers, flashing red and green, push notifications on 1% moves, banners telling you what to do next. None of that changes the data. The chart up top samples prices every two and a half minutes, draws itself when you load the page, and stays quiet between visits. That's the only correct cadence for price information someone checks out of curiosity rather than obligation.
If the same approach appeals for things that aren't crypto, Retired Today has a handful of calm apps built the same way — a dumbbell-only home workout tracker and a markdown-first task sheet. Same design: no notifications, no tracking, the site updates when you load it and stays silent when you don't.
For live single-asset reads of the two coins separately — what each is at right now plus the path of the last 12 hours — see the BTC-to-USD live converter and the ETH-to-EUR live converter.
FAQ
Why 12 hours as the window?
Long enough to span at least one trading session (Asian, London, or New York) and usually show a full session handoff. Short enough that the rebased percentages still reflect "current regime" rather than ancient history. 24h would be fine too but starts to smear multiple regimes into one chart; 4h is too short to see slower separations build. Twelve is the middle-ground pick most analysts default to.
Why do the lines start at exactly the same point?
That's what "rebased to zero" means — both lines are zeroed at the first sample in the window, by subtracting each coin's starting price from every subsequent price and dividing by the starting price. It's a mathematical construction, not a market phenomenon. The information in the chart is entirely about how they diverge (or don't) from that shared zero.
Is a 2% spread big? What counts as "significant" divergence?
Rules of thumb from years of looking at these: under 0.5% is noise, 0.5% to 1.5% is normal variation, 1.5% to 3% is worth noting (often corresponds to a specific event), above 3% is unusual and worth a search for what's driving it. These shift over time as baseline volatility changes — they were narrower in the low-volatility second half of 2024 and wider through 2022's cascading events.
Does BTC always lead and ETH follow?
No. It used to be more reliable — roughly 2017-2020 — that BTC moved first and ETH amplified the move. Since then, ETH has increasingly moved on its own catalysts (upgrades, regulatory decisions, gas-economy shifts). Today either can lead on any given day, and the direction of the lead is often itself the story.
What about SOL and other large caps — are they similar?
Broadly yes — SOL, BNB, AVAX, and the other top-ten caps track BTC closely and share most of the same forces described above. The correlation weakens as you go further down the liquidity ladder. By the time you're looking at rank 50+, individual coins routinely do their own thing for reasons that have nothing to do with the broader market.
Why cyan for ETH specifically?
Ethereum's brand colour has historically been a blue-purple, but for on-chart readability against the platform's gold accent, a bright cyan gives maximum contrast without clashing. The rest of the platform uses the same cyan (#4FD4E3) for "important / special" markers — the orbit visualisation, the home-screen particle cloud — so dual-line charts inherit the same palette convention. BTC stays on the gold accent.
Can I export this chart or link to a specific time window?
Not yet. The chart is rendered server-side as an SVG and embedded directly in the post HTML, so saving the page saves the chart as of that load, but there's no URL-parameter interface to pick a different window or export raw data. That's a deliberate simplicity — this is a reader's view, not a trader's terminal.
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