Freehand optical coherence tomography (OCT) systems without mechanical scanners can offer greater freedom to access and image sites of interest. However, the scanning velocity during freehand scan is irregular; therefore pseudo B-scan images obtained by stacking sequentially acquired A-scans have a non-uniform spatial sampling rate in the lateral dimension. In this study, we developed a speckle decorrelation method to estimate lateral displacement between sequentially acquired A-scans and used the information extracted from speckle analysis to correct the time-varying lateral scanning speed. We applied this method to a handheld OCT probe and performed calibration experiments to validate our model. Furthermore we demonstrated distortion-free, freehand OCT imaging of various samples including human tissue, in vivo.