We've had some questions regarding the dimensions of the Tilt Hydrometer. How big is the Tilt Hydrometer? Will it fit in my fermenter? The device is 3 5/8 inches (9.2075 cm) long by 1 1/8 inch (2.8575 cm) in diameter. It is designed to fit in a typical carboy. Here are a couple pictures with a Quarter and an iPhone to give some perspective.