Strain sensors provide a critical function in determining whether or not an aircraft is safe to fly or must be retired. Specifically, strain sensors are utilized on inservice aircraft to obtain the load histories of various parts and structures. This load history data is then used by structural fatigue life tracking methods to determine how much structural life has been consumed and to make decisions regarding the ability to safely operate the aircraft. However the usefulness of the strain data can be compromised by the inability to consistently manufacture and install the sensors, and aircraft-to-aircraft variations in the structures themselves. As such, variations in strain readings greater than 10% are typical in aircraft applications. This variation must be accounted for in order to improve fatigue life tracking and enhance decisions on the sustainability of the aircraft. Frequent and accurate calibration is thus necessary to ensure accurate aircraft fatigue usage estimates, which will in turn reduce the need/cost of purchasing new aircraft (resulting from the retiring of aircraft with remaining useful life) and, more importantly, reducing the risk associated with flying unsafe aircraft. However, current strain sensor calibration methods are inadequate. For example, the ideal calibration approach involves placing the entire aircraft in a full scale test rig and applying known loads to the structure. This approach is extremely expensive and time-consuming when performed on an aircraft-to-aircraft basis. Alternately, the aircraft could be flown in tightly prescribed maneuvers where loads can be fairly well determined. However, this approach is far less accurate and in some cases, it is difficult to prescribe repeatable maneuvers (loads) for certain sections of the aircraft. As such, a need exists for a cost/time-effective means to calibrate strain gauges on each aircraft with an accuracy that is comparable to the full scale test rig approach. To address these issues, the authors are developing an innovative strain sensor calibration system that uses a portable device to (1) apply a low level and localized dynamic load near the strain gauge, (2) measure the load and structural responses from an integrated force sensor and the strain gauge itself, (3) evaluate the measurements relative to a reference structure, and (4) provide a calibration factor for each individual strain sensor. This paper presents an overview of the approach and describes experimental results for both baseline (static) and dynamic excitation tests, including the implemented test and analysis procedures. The authors also identify and evaluate various factors that affect the accuracy of the approach, including load repeatability, sensor configuration, excitation force, measurement error, data acquisition considerations, analysis methods, etc. An accuracy goal of 1% has been set for the calculated calibration factors on simpler structures and 2% on trial parts of increasing complexity. Tests were thus conducted to verify test repeatability and evaluate calibration accuracy.