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How Currency Strength Works and When It Matters

Human · 16 min read
How Currency Strength Works and When It Matters

Why currency strength matters

Every forex quote is a ratio, and a ratio hides which side moved. When EUR/USD rises 1%, the euro may have strengthened, the dollar may have weakened, or both may have moved at once. The chart looks identical in all three cases. The trade does not.

Currency strength analysis solves that problem by measuring each currency against a basket of the others instead of against one counterpart. It turns 28 overlapping exchange rates into eight readings, one per major currency, and tells you where the pressure in the market actually sits.

This article argues a narrower point than most strength-meter marketing. Currency strength is an excellent way to describe the market and a conditional, timeframe-dependent way to predict it. Used on the right horizon it captures a real, documented effect. Used on the wrong one, or stacked into a "confluence" score, it mostly measures noise.

What is currency strength?

Currency strength is a measure of how one currency has performed against a group of other currencies over a defined period. It answers "what did the yen do?" rather than "what did USD/JPY do?"

The idea is not new. Central banks and statistical agencies have long published effective exchange rate indices, which weight a currency against its trading partners. The US Dollar Index (DXY) is a familiar example, though its fixed basket is dominated by the euro, at roughly 58% of the weight. A rising DXY can therefore say more about the euro than about the dollar's performance against the yen or the Australian dollar.

Retail currency strength meters usually take a different approach. They compare each major currency against every other major currency with equal weight, so no single counterpart dominates the reading.

Three distinctions matter before you read any strength chart:

  • Change, not level. Almost every meter measures recent returns, not whether a currency is cheap or expensive. A "strong" currency in this sense has been rising, which is different from being overvalued.
  • Relative, not absolute. Strength is measured only against the other currencies in the basket. If everything falls against the dollar, the dollar is strong by definition.
  • Horizon-specific. A currency can be the strongest on a four-hour chart and the weakest on a weekly one. A strength reading without a lookback period attached is incomplete.

How a currency strength meter is calculated

A standard currency strength meter starts from the eight major currencies: USD, EUR, JPY, GBP, AUD, CAD, CHF and NZD. Those eight form 28 unique pairs, and each currency appears in exactly seven of them.

For each currency, the meter takes its return against each of the other seven over a lookback window, flips the sign where the currency is the quote rather than the base, and averages the result. Written with log returns:

S_c = \frac{1}{7} \sum_{j \neq c} \ln\left( \frac{P_{c/j,\,t}}{P_{c/j,\,t-k}} \right)

Here S<sub>c</sub> is the strength of currency c, P<sub>c/j</sub> is the price of c in units of currency j, t is the current bar and k is the lookback length. Log returns are used because they invert cleanly: the log return of USD/JPY is exactly the negative of the log return of JPY/USD, so the sign flip introduces no distortion.

One consequence follows directly from the arithmetic. Every pair's return is counted once as a gain for one currency and once as a loss for the other, so the eight strength scores sum to zero. Strength is a zero-sum ranking. One currency can only gain at the expense of the others.

A worked example with three currencies

Suppose that over one week EUR/USD falls 0.5% and USD/JPY rises 1.0%. Because exchange rates must be consistent with one another, EUR/JPY rises by roughly 0.5% (−0.5% + 1.0%).

Currency vs first vs second Strength (average)
USD +0.5% vs EUR +1.0% vs JPY +0.75%
EUR −0.5% vs USD +0.5% vs JPY 0.00%
JPY −1.0% vs USD −0.5% vs EUR −0.75%

The scores sum to zero, as they must. The useful insight is in the middle row. EUR/JPY rose 0.5%, yet the euro itself was flat. The entire EUR/JPY move was yen weakness. A trader who bought EUR/JPY believing in euro strength would have been right about the price and wrong about the reason, which matters the moment the yen reverses.

The design choices that change the answer

There is no industry-standard meter, and small methodological choices can reorder the rankings:

  • Lookback length. A 20-bar window and a 200-bar window measure different things and frequently disagree.
  • Volatility normalisation. NZD and JPY crosses tend to move more than EUR/CHF. A raw average lets high-volatility currencies dominate the extremes. Dividing each return by its own recent volatility puts currencies on a comparable scale.
  • Weighting. Equal weighting treats NZD/CHF like EUR/USD. Turnover weighting reflects where liquidity actually sits but lets the dollar and euro crowd out the rest.
  • Price timing. Closes at different times across feeds, or bid prices against mid prices, introduce small but systematic differences.

When two meters disagree, the cause is usually one of these four, not the market.

What drives currency strength?

A strength meter records the outcome. To use it well, you need a view of what produced that outcome, because different drivers persist for different lengths of time.

Expected interest-rate differentials

The most durable driver is the expected path of interest rates, not the current policy rate. If markets begin pricing more rate hikes in Australia than in Japan, the expected return on holding Australian dollar assets rises relative to yen assets. Investors who act on that gap buy AUD and sell JPY, and both strength readings move. Short-dated government bond yields, such as two-year yields, are a reasonable proxy for these expectations because they move as rate pricing shifts.

This is also why strength often trends. Central banks change direction slowly, and markets reprice that direction in stages rather than all at once.

Capital flows and the carry trade

A carry trade borrows in a low-yielding currency and invests in a higher-yielding one, earning the difference as long as the exchange rate cooperates. For years the yen has been a common funding currency for this trade. The mechanism links strength readings across the market: when carry positions build, funding currencies weaken steadily. When they unwind, often abruptly, those same currencies can top the strength table within days.

Risk appetite

Currencies sort roughly into two groups by how they behave when markets turn defensive. The yen, Swiss franc and often the US dollar tend to strengthen in risk-off episodes. The Australian, New Zealand and Canadian dollars, tied more closely to global growth and commodity demand, tend to weaken. A single risk-off session can therefore reshuffle the whole strength table without any change in national fundamentals. These moves are real, but they are often short-lived.

Terms of trade and data surprises

Commodity exporters' currencies respond to the prices of what they sell: the Canadian dollar to oil, the Australian dollar to metals, the New Zealand dollar to dairy and other agricultural exports. Economic releases matter too, but only relative to expectations. A strong employment report that was fully forecast moves little. A modest one that beats a pessimistic consensus can move a lot.

Why the US dollar distorts every reading

The dollar's role in the market is structural, not incidental. The Bank for International Settlements' 2025 Triennial Survey found that global FX turnover reached $9.6 trillion a day in April 2025, and that the dollar was on one side of 89.2% of all trades. The euro followed at 28.9%, the yen at 16.8% and sterling at 10.2%. Because each trade involves two currencies, these shares sum to 200% (BIS press release; BIS survey commentary). The April 2025 figures were also collected during a month of unusually high volatility after US trade-policy announcements, which likely boosted turnover.

For strength analysis, the implication is that a large dollar move shows up twice: as dollar strength and as apparent weakness in every other currency. Before concluding that six currencies are weakening together, check whether one currency is simply moving against all of them.

Does currency strength predict price direction?

Sometimes, on some horizons, with a smaller edge than most strength-meter marketing implies. The honest answer depends on which question you ask.

What the academic evidence says

Ranking currencies by recent performance and buying the winners against the losers is a strategy finance researchers call cross-sectional currency momentum. A currency strength meter is, in effect, the first half of that strategy: the ranking.

The most cited study is Menkhoff, Sarno, Schmeling and Schrimpf (2012) in the Journal of Financial Economics. Using data from 1976 to 2010, they found a spread in excess returns of up to 10% a year between past winner and loser currencies (City, University of London repository). The spread was not explained by standard risk factors and behaved differently from the carry trade, which suggests momentum is a distinct effect rather than carry in disguise.

The same paper also contains the caveats that matter most for retail traders:

  • Transaction costs explained part of the returns.
  • The authors found significant limits to arbitrage, meaning the effect was hard to exploit in practice.
  • The returns were concentrated in a broad universe that included many less liquid currencies. In an interview at publication, Sarno noted that trading momentum in the major currencies alone would have lost money over the last decade of their sample (Hedgeweek).

That last point deserves emphasis. The headline 10% does not transfer directly to a meter built on eight majors. It is evidence that the phenomenon exists, not a performance estimate for any particular indicator.

Why the timeframe decides almost everything

The signal-to-noise ratio of currency returns falls sharply as the horizon shortens. A persistent drift of a few basis points a day is invisible against daily moves driven by data releases, headlines and order flow. Over a week, the noise partly averages out and slower drivers, such as shifting rate expectations, have time to show through. Transaction costs also weigh more heavily on short horizons, because the expected move per trade is smaller while the spread stays the same.

Pipnotic's own backtests point the same way. Testing strength-based momentum across 59 pairs with data back to 2017, we found that weekly strength momentum held up across the sample, while daily strength momentum was statistically indistinguishable from noise. This is one reason the Weekly Bias panel uses weekly readings and fixed backtest boundaries rather than intraday strength.

The confluence trap

A common practice is to treat agreement across timeframes as conviction: if a currency is strongest on every chart you check, the signal must be strong. Our testing found the opposite. Across the four timeframes we tested, setups where all four agreed were the worst-performing group.

We can describe that result with confidence. Its cause is less certain. One plausible explanation is that full agreement tends to occur late in a move, after the currency has already travelled far and positioning has become crowded, which leaves more room for a pullback than for continuation. Whatever the mechanism, "more indicators agree" is not the same as "more likely to work", and it should be tested rather than assumed.

How to use currency strength in forex trading

Currency strength is most useful as a decision aid for what to trade and why it is moving, and least useful as a trigger for when to enter. Five practical uses follow from the mechanics above.

  1. Pair the strongest with the weakest. If USD is at the top of the weekly table and NZD at the bottom, NZD/USD expresses the widest differential available. Pairing two strong currencies, such as USD and CHF, produces a pair whose two halves are pulling in the same direction and largely cancel out.
  2. Diagnose before you trade. Before buying EUR/JPY, check whether the move came from the euro, the yen or both. As the worked example showed, a pair can rise on one currency's weakness while the other is flat. The answer tells you which news, central bank and risk events can reverse the trade.
  3. Choose the horizon deliberately. Use the timeframe on which the signal has shown persistence, which for most strength measures means weekly or longer, as the directional bias. Use shorter charts for execution and risk placement, not for direction.
  4. Count your currency exposure, not your pairs. Long EUR/USD, long GBP/USD and short USD/CHF look like three trades. They are one large short-dollar position. Strength analysis makes this visible: if all three were chosen because USD is weak, a single dollar reversal hits all three at once. Size accordingly.
  5. Ask what is driving the reading. Strength built on a repricing of the rate outlook tends to last longer than strength built on one risk-off session. A strength table cannot tell you which you are looking at. Rate expectations, the economic calendar and risk sentiment can.

A strength reading should change which trades you consider and how much you risk on them. It should not replace a defined entry, a stop-loss and position sizing based on volatility.

Limitations and common mistakes

The limits of currency strength follow from how it is built. Knowing them prevents most of the expensive misreadings.

  • It is backward-looking by construction. A strength score is a summary of past returns. Any predictive value rests entirely on those returns persisting, which is an empirical question, not a property of the indicator.
  • It is relative, so one currency can distort the rest. Because the scores sum to zero, a sharp move in one currency, most often the dollar, pushes every other score the opposite way. Seven "weak" currencies may simply be one strong one.
  • Unnormalised meters over-rank volatile currencies. Without volatility scaling, the currencies that move most will occupy the extremes of the table most often, regardless of whether their moves are more persistent.
  • Policy can override trend. Strength readings can reverse in a session when authorities act. Japan's Ministry of Finance intervened to support the yen in 2022 and again in 2024, abruptly lifting a currency that had sat near the bottom of strength tables for months.
  • Confluence is not conviction. Stacking agreement across timeframes feels rigorous but, in our testing, selected the worst entries. Treat any composite score as a hypothesis until it has been backtested out of sample.
  • Optimising the lookback is a route to overfitting. Testing dozens of window lengths and keeping the best one almost guarantees a backtest that looks better than live trading will. Fix the method first, then test it.
  • Costs scale with ambition. Crosses and exotic pairs often carry wider spreads than the majors. A strategy that rotates through the strongest and weakest pairs every week can spend a meaningful share of its edge on execution.

Currency strength FAQ

What is currency strength in forex?

Currency strength measures how a single currency has performed against a basket of other currencies over a set period. Instead of reading one exchange rate, such as EUR/USD, it shows whether the euro or the dollar was responsible for the move. Most meters cover the eight majors: USD, EUR, JPY, GBP, AUD, CAD, CHF and NZD.

How is a currency strength meter calculated?

A typical meter calculates each currency's return against the other seven majors over a lookback period, inverting returns where the currency is quoted second, and averages them. Log returns are preferred because they invert symmetrically. Better meters also scale each return by recent volatility so that naturally volatile currencies do not dominate the rankings.

What is the best timeframe for currency strength?

Longer horizons generally carry more signal than shorter ones. Daily and intraday strength is dominated by news and order flow, and in Pipnotic's backtests daily strength momentum behaved like noise. Weekly strength showed persistence. A practical approach is to use weekly strength for directional bias and shorter charts only for timing entries and exits.

Do currency strength meters work?

They work well as a description of where pressure sits in the market. As a predictor, the evidence is mixed. Academic research documents real cross-sectional momentum in currencies, but it is sensitive to transaction costs and concentrated outside the majors. Results depend heavily on timeframe and method, so any strength strategy should be backtested before it is traded.

What is the difference between currency strength and the DXY?

The US Dollar Index measures the dollar against a fixed basket of six currencies weighted heavily towards the euro, at about 58%. A currency strength meter typically measures every major currency, not only the dollar, and weights each counterpart equally. The DXY can rise mainly because the euro fell, while a strength meter separates the two.

Which currency is the strongest right now?

That changes continuously and depends on the timeframe you use. A currency can lead on a four-hour chart while lagging on a weekly one. Check a live strength reading for the horizon you trade, and confirm what is driving it before acting on it.

The real power of currency strength

The power of currency strength is not that it predicts the market. It is that it shows you what an exchange rate hides. A pair is two currencies, each with its own central bank, its own capital flows and its own sensitivity to risk. Strength analysis separates them, so you can see which one is moving, why, and how many of your positions depend on it.

Used on a horizon where the signal persists, such as weekly, it captures a momentum effect that academic research has documented across decades of data. Used on noisy horizons, or compressed into a confluence score, it measures little beyond recent volatility. The difference between those two outcomes is not the indicator. It is whether the method has been tested.

Pipnotic publishes the results of its strength backtests, including the signals that failed. Create a free account to see the live Weekly Bias readings.

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