Question: what size wrench bike pedal?
Answer: Pedal wrench flats are typically 15mm in size. 9/16" (~14.3mm) is somewhat common on older pedals. 17mm and other sizes have been used, but you aren't very likely to encounter them. (A "cone wrench" is thinner and shorter than a pedal wrench, and unable to provide appropriate durability or leverage for use on pedals.