No hard or fast rule here, all down to the product you are trading, whether you are long term, short term, or day trading. A lot of hard work identifying what level of stop is required, imho not just use a % of capital. EG: if you data says a stop of 17 will suffice to allow a position to build whilst the price movement fluctuates up and down, use that figure as a disaster stop, why set it higher?, you will lose capital very quickly if you do. Its not easy getting, but with lots of hard work and data crunching you should come up with a figure for protecting position that has gone wrong.