About back-EMF constant

Hello! I want to ask, how many back-constant is this type of brushed DC motor?

https://www.robotshop.com/uk/lynxmotion-12v-90-rpm-9911oz-in-1269-brushed-dc-gear-motor-w--encoder.html

Hello @HL123 !

Welcome to the forum. I guess you’re looking for the Back-EMF constant. I certainly didn’t find it in the motor specifications and no product datasheet is shown. Maybe @AudioVOX or @igor_X could help us with this.