There is no single standard for PCBs, but Costar-made keyboards (Filco Majestouch, WASD, CM Quickfire Rapid) have a common format though: 0.5 unit vertically between F-keys and numeric row, 0.25 unit horizontally between F12 and Print Screen columns. Parts made for these keyboards fit these measurements.
The KBD8X PCB for instance, does not adhere to Costar's measurements.