A strain sensor having an active area that includes a magnetoelastic resonator and spring configured so that the spring undergoes a greater amount of strain than the resonator when the sensor is under load. The sensor is anchored at opposite ends of the active area to a substrate for which strain is to be measured. An interrogating coil is used for wireless sensor readout. A biasing magnet may be included to provide a desired sensor response for the particular application of the sensor. The strain sensor may be implemented as a differential strain sensor that includes a second, strain-independent reference resonator.