The present invention detects the squaring and feathering of an oar during rowing. The time interval between two consecutive feathers is measured, and it is used to calculate the stroke rating. It is mounted to an oar close to the grip of the oar. An enclosure houses a display, a sensor, a microcontroller, a power source and a clock which is a component of the microcontroller. The stroke rating is displayed on a display. A strap is attached to the enclosure. The strap fastens the enclosure to the oar. The direction of the rotation of the oar from the squared position to the feathered position is shown by the arrow. Because of its small size, the device does not hinder rowing while remaining in plain view of the rower, and because it does not use any external or rigidly mounted sensors it can easily be transported and used on various equipment.