May be you are not getting my point. Suppose I have collected siRNA from Journal. Now I want to find the gene silencing efficacy of that particular siRNA. Can it be possible?
Prediction of its silencing efficiency is hard to find using software or online tools, you can only find if your sequence is homologous to some other sequences by simply BLASTing it.
The efficiency of silencing will also depend on how much siRNA you actually get into the cell.. So, your transfection efficiency is also very important, and can vary between cell lines.
I don't think there is a way to find out using a computer.... (if it was possible, then all siRNAs companies make would be specific & on-target etc, and all would silence very well.....)