Slippage on Thin Pairs, Measured Rather Than Estimated

Slippage is the difference between the best available price and the average price you actually paid across an order. On thin pairs it dwarfs every fee.

Method

Read the order book before the trade. Sum the available quantity at each price level until you reach your order size. The weighted average of those levels is your expected fill.

Compare that against the top of the book. The difference is the slippage you are about to accept, calculable in advance and almost never calculated.

What depth looks like at two extremes

On a major pair at a large venue, several hundred thousand dollars can sit within a tenth of a per cent of the top. An order of a few thousand moves nothing measurable.

On a thin pair, the first few thousand dollars can clear several price levels. The same order size produces slippage of a per cent or more.

The table worth building once

Order size	Levels consumed	Average fill vs top
Small	One	Negligible
Medium	Two to four	Tenths of a per cent
Large	Many	Whole per cents

Fill it in for the pairs you actually trade, from the live book, at the time you trade. The numbers are specific to the venue and the hour.

Why the fee schedule misleads here

A venue advertising a lower trading fee on a thin pair is advertising the smaller of the two costs. The book decides the larger one.

Comparing fee schedules between a deep venue and a shallow one is comparing the wrong column.

What reduces it

Limit orders instead of market orders, which cap the price at the cost of possibly not filling. Splitting the order across time, which lets the book refill. And trading in active hours, when depth is greatest.

Splitting across venues helps only if each venue has independent depth, which for small pairs it often does not.

What makes it visible in advance

A venue that shows the expected fill, not just the top price. Platforms that show slippage before confirmation turn this measurement into a number on the screen.

Where that is not shown, the book is still public and the arithmetic takes a minute. A platform where the spread is visible before the trade is the shortcut, and on thin pairs it is worth more than any fee difference. For anything large, Collect & Exchange, where the quote holds for the whole amount, removes the question by quoting the whole size at once.