The US dollar index (DXY) closed on Monday 12 October 2026 at 102.58, its highest daily close in the past 12 months of Yahoo Finance data and 6.6% above its 27 January low of 96.22. Babypips reports that the dollar gained against all seven major currencies that day (Babypips, 12 October 2026), and the euro touched a new 2026 low of 1.1155 (investingLive wrap, 12 October 2026). Bitcoin fell 2.3% on the same day. That raises an obvious question for anyone holding bitcoin into Wednesday’s CPI report: does a stronger dollar reliably hurt it? This desk tested it on 250 trading days of its own data.
The test
We paired Coinbase Exchange daily closes for bitcoin (UTC day) with Yahoo Finance daily closes for the dollar index (DX-Y.NYB) for every day from 14 October 2025 to 12 October 2026 on which both series have a value and the previous day’s value, which gives 250 paired days. For each day we took the dollar’s close-to-close change and bitcoin’s close-to-close change, then grouped days by the size of the dollar move. The dollar index trades Monday to Friday, so for each dollar day we measured bitcoin from the close of the previous dollar trading day: a Monday’s bitcoin change therefore spans Friday’s close to Monday’s close, three calendar days. The bitcoin day ends at 00:00 UTC (8 p.m. New York) and the dollar index closes earlier in the New York afternoon, so the windows overlap but are not identical. “Standard error” (SE) below is the standard deviation of the daily returns divided by the square root of the number of days, which tells you how much an average of that size could wobble by chance.
The result: bitcoin’s bad days cluster on strong-dollar days
| Dollar index move | Days | Bitcoin average daily change | Standard error | Days bitcoin rose |
|---|---|---|---|---|
| Rose 0.3% or more | 42 | −1.33% | 0.31 pts | 11 (26%) |
| Rose 0.4% or more | 23 | −1.09% | 0.49 pts | 8 (35%) |
| Rose 0.5% or more | 17 | −1.36% | 0.60 pts | 5 (29%) |
| Between −0.3% and +0.3% | 168 | +0.11% | 0.22 pts | 83 (49%) |
| Fell 0.3% or more | 40 | +0.30% | 0.42 pts | 22 (55%) |
| Fell 0.4% or more | 26 | +0.41% | 0.55 pts | 16 (62%) |
| Fell 0.5% or more | 17 | +0.94% | 0.78 pts | 12 (71%) |
| All 250 days | 250 | −0.10% | 0.17 pts | 116 (46%) |
On the 42 days the dollar index rose at least 0.3%, bitcoin rose only 11 times and averaged −1.33%, with a median of −1.57%. On the 40 days it fell at least 0.3%, bitcoin averaged +0.30% and rose on 22 of them. The gap between the two groups is 1.63 percentage points, about three combined standard errors (the square root of 0.31² plus 0.42² is 0.52), which is unlikely to be pure noise. The pattern also gets stronger as the threshold rises: when the dollar rose 0.5% or more, bitcoin rose on only 5 of 17 days, and when it fell 0.5% or more, bitcoin rose on 12 of 17 and averaged +0.94%. The overall correlation of daily changes is −0.18 over the full 250 days, −0.31 over the last 120 and −0.29 over the last 60: negative, modest, and strengthening.
How much of that is a handful of days?
Two outlier checks. Dropping the two worst and two best bitcoin days from each of the two groups leaves the dollar-up average at −1.36% across 38 days and the dollar-down average at +0.30% across 36 days, so the result is not driven by a few extreme sessions. But the sample is not evenly spread: 11 of the 42 dollar-up days fall in March 2026, a single volatile month, and the series also contains plenty of days that break the pattern. The three worst bitcoin days on dollar-up sessions were 2 February 2026 (dollar +0.64%, bitcoin −6.47%), 4 November 2025 (+0.35%, −4.78%) and 5 June 2026 (+0.66%, −4.35%), but the single best dollar-up day was 2 March 2026 (+0.79% for the dollar, +4.51% for bitcoin). And the worst bitcoin day among the dollar-down sessions was 20 January 2026: the dollar fell 0.75% and bitcoin fell 7.53%.
That is why this is a tendency, not a rule. A stronger dollar is often a symptom of something else — higher expected US interest rates, a risk-off flight to cash, an oil-driven inflation scare — and it is those drivers, not the currency itself, that bitcoin may be reacting to. The most recent examples fit that reading. On 7 October the dollar rose 0.40% and bitcoin fell 2.65%, in the week the 10-year Treasury yield reached its highest since 2002, which we covered in our study of yields and bitcoin. On 12 October the dollar rose 0.36% and bitcoin fell 0.97% measured from Friday’s close (2.3% on Monday alone). Since 1 September the pattern has been too thin to say much: seven dollar-up days with a bitcoin average of −0.63% (SE 0.63, three up days), and four dollar-down days averaging +0.75% (SE 1.29, one up day).
What it means for Wednesday’s CPI
The dollar’s rally and the oil move are one story. Higher energy prices push up headline inflation, the Fed is already at 3.75%–4.00% after its 16 September hike, and the September minutes showed most officials see another hike as appropriate by year-end, per Babypips. The consensus for September CPI is about +0.6% on the month and 3.6%–3.7% on the year, with core at +0.2% (FinancialJuice and investingLive tables, 11–12 October). If that is delivered, the dollar-and-oil story is already priced and the market’s attention shifts to core. A core reading at or above 0.3% would strengthen the case for an October hike, which would tend to lift the dollar again; a reading at 0.2% or below would do the opposite. Based on the last year of data, the dollar’s reaction is a better guide to bitcoin’s day than the headline number itself — but only as a tilt: even on the strongest dollar days in the table, bitcoin rose roughly one time in four.
Our earlier study, What Bitcoin Did on the Last Seven CPI Mornings, found a four-hour range of 2.8% on CPI mornings against 1.7% on an ordinary day. Combining the two: expect a wider range than usual and a direction that, historically, has leaned with the dollar. For the oil link, see our analysis of Brent and bitcoin, which found essentially no daily correlation (−0.08) over 247 days — a reminder that the dollar relationship is stronger than the oil relationship, not that either is dependable.
Limitations
This is a one-year, daily, two-variable study. It does not control for yields, equities or oil, so it cannot separate the dollar’s effect from the things that move the dollar. Days are not independent — macro shocks cluster — so the standard errors above are probably too small. The windows for the two assets do not match exactly. We report all thresholds we tested (0.3%, 0.4% and 0.5%) and no others. And a past-year pattern is a description of what happened, not a forecast of what will.
Method: bitcoin and ether prices, highs, lows and closes are Coinbase Exchange candles (UTC day or UTC hour) pulled by Bitcoin Mastery at about 06:15 UTC on Tuesday 13 October 2026; the 13 October candle is still open at that time, so any closing figure quoted is the 12 October close unless stated. Dollar-index and Brent figures are Yahoo Finance daily closes (DX-Y.NYB and BZ=F continuous front-month); other third-party figures are attributed to their source and date. The dollar-index series (DX-Y.NYB) is Yahoo Finance data and the 13 October dollar value (102.37) is an intraday print, excluded from the study.
Disclaimer: This article is for informational purposes only and does not constitute investment advice. Bitcoin and other cryptocurrencies are volatile and you can lose some or all of the money you put in. Nothing here is a recommendation to buy, sell or hold bitcoin, any exchange-traded fund, any listed security or any other asset, and the technical levels, probabilities and scenarios discussed are descriptions of published data, not forecasts. Do your own research and consult a licensed financial advisor before making investment decisions.