Currency Strength, Explained: How to Read the FOTSI Oscillator?

Every pair is a tug-of-war between two currencies — the FOTSI oscillator isolates each one's momentum so you can see which side is actually driving the move.

A Pair Is Two Forces

When EUR/USD rises, the price alone never tells you why. Is the Euro strong, or is the Dollar weak? You are only seeing the net result of two currencies pulling against each other. To trade with the trend, you want to know which side is doing the work.

What "Strength" Really Means Here?

A currency strength meter answers that by stripping each currency out of its pairs and measuring its own momentum. FOTSI — the Forex Oscillator of True Strength Index — is one, and it does this for the eight majors: USD, EUR, GBP, JPY, CHF, AUD, CAD, and NZD.

Under the hood it reads the momentum of all 28 major-currency combinations, attributes each move to the currencies involved, and smooths the result with the True Strength Index, a double-smoothed momentum measure. The output is eight lines on one chart — one per currency.

Reading the Oscillator

FOTSI oscillates around a zero line, with extreme zones marked at +50 and −50:

• Above +50 — the currency is overbought. Momentum is stretched, so a correction or pullback becomes more likely and chasing fresh longs on its pairs is risky.
• Below −50 — oversold, the mirror image.
• Zero-line cross — momentum has flipped sign. A new trend may be forming for that currency's pairs.
• Divergence between two lines — when one currency climbs while another falls, the pair built from them has the cleanest trend. That is the textbook setup the oscillator points to.

Strong vs Weak, Paired Up

The practical edge is pairing the strongest currency against the weakest. If the Dollar sits near the top and the Yen near the bottom, USD/JPY is where the two momentum readings reinforce each other — a continuation setup rather than a fight against one strong side.

What FOTSI Is Not?

It is a momentum and strength gauge, not a buy or sell signal. Overbought can stay overbought in a powerful trend, and a zero cross can fail. FOTSI tells you where the momentum sits and which pairs line up cleanly; confirmation, entries, and risk are still your job — and it reads best alongside the day's news and the calendar, never in isolation.