Disclosed herein are systems, methods, and apparatus for calibrating contrast measurements from laser speckle imaging systems to accurately determine unknown particle motion properties, such as flow rates. The calibration step stores to memory calibration data, which may include a set of measurements and / or noise estimates from a sample with known particle properties, including effects on contrast caused by undesired signals unrelated to unknown particle motion properties . Calibration data can be accessed and used to correct empirical measurements of contrast and / or to interpolate values for unknown particle motion properties. The system may include a light source, light detector, processor, and memory that may be combined into a single device, such as a wearable device, for providing calibrated flow measurements. The device can be used, for example, to measure blood flow, cardiac output and heart rate, and can be used to amplify pulsatile signals.