We present an analytical relation between the position estimation uncertainty and inertial measurement unit (IMU) characteristics during zero-velocity-update (ZUPT) augmented pedestrian inertial navigation. The effect of angle random walk of gyroscopes and velocity random walk of accelerometers in IMU on circular error probable is studied. Numerical simulation of the ZUPT-augmented navigation algorithm is conducted based on a generated pedestrian trajectory to verify the analytical results, showing the discrepancy less than 15, which supports the fidelity of the results. Experiments are also conducted, and the results match our analytical prediction, with the error less than 20. This study offers a closed-form analytical expression to predict the performance of ZUPT-augmented pedestrian inertial navigation.