A novel capillary-action microfluidic viscometer has been designed that can measure the relative viscosity of a sample compared to a control liquid. Using capillary action circuits, the viscosity of a sample is transformed into an easy-to-read comparative bargraph format while using no external instrumentation. This implementation is made practical through capillaric Field Effect Transistors, and the automated valving they enable. Using poly-ethylene glycol solutions as viscous samples, we demonstrate that the device can transduce the relative viscosity of a sample and control material consistently to within 2% in less than 5 minutes of measurement time. In addition, we show that the device can partially account for temperature through internal referencing. In the future, this device could be applied to medical care, quality assurance, and scientific measurements.