Triangular arbitrage keeps cross rates honest, and scalpers can use that

[Amanhasnoname]

EURUSD, GBPUSD and EURGBP are linked. If two of them move, the third must follow, or someone with fast systems captures the difference in microseconds.

That relationship limits how far a cross can drift from the implied rate. For retail traders, it means the cross rarely lags for long. But in the moments after a big move in one leg, quotes on the cross may briefly lag, and spreads on the cross widen to protect liquidity providers.

A scalper watching all three can sometimes notice that the cross hasn't caught up yet. Acting on it is another matter, because those windows are usually too short for retail execution and the spread on the cross eats the difference.

Still, the idea helps in interpretation. If EURUSD jumps and EURGBP hasn't moved, either GBPUSD jumped too or the cross is about to adjust.

Monitoring implied versus actual cross rates is easy to set up in a spreadsheet or indicator.

Does anyone track implied cross rates as part of their routine?