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Why size matters a lot in trading

It’s reality check time: do you find yourself focusing almost entirely on the entry price, ending up underestimating the entry size? You are not alone in this. In the frenzy of finding the perfect entry point, entry size is often neglected with the majority of traders ending up trading too big.

The problem with this is that the larger the size, the more likely you are to exit a good trade on a meaningless adverse price move, as fear (rather than judgement and experience) takes the decision.
Considering that we don’t know if the next trade is a winner or a loser, it is a useful rule of thumb to risk no more than 1% or 2% of the capital on each individual trade, in order to be easily able to make up losses in case the market moves in an unfavorable way.

Defining the amount one can afford to lose and the price level that invalidates the trading strategy allows a trader to calculate the right position size. For example, if you are willing to risk £1000 per trading idea and your stop is £2 below/above entry, you can afford 500 shares.

Or to put it in the words of the Sage of Omaha, Warren Buffett: ‘Risk comes from not knowing what you are doing.’

Dafni Serdari
Market Analyst

Published: 10 June 2014

You should under no circumstances consider the information and comments provided as an offer or solicitation to invest. This is not investment advice. The information provided is believed to be accurate at the date the information is produced.

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