A device to measure density (weight) of mud, cement or other liquid or slurry. A mud balance consists of a fixed-volume mud cup with a lid on one end of a graduated beam and a counterweight on the other end. A slider-weight can be moved along the beam, and a bubble indicates when the beam is level. Density is read at the point where the slider-weight sits on the beam at level. Accuracy of mud weight should be within +/- 0. 1 lbm/gal (+/- 0. 01 g/cm³). A mud balance can calibrated with water or other liquid of known density by adjusting the counter weight. Most balances are not pressurized, but a pressurized mud balance operates in the same manner.