This paper presents the fundamental mathematics to determine the minimum crack width detectable with a terrestrial laser scanner in unit-based masonry. Orthogonal offset, interval scan angle, crack orientation, and crack depth are the main parameters. The theoretical work is benchmarked against laboratory tests using 4 samples with predesigned crack widths of 1-7 mm scanned at orthogonal distances of 5.0-12.5 m and at angles of 0 -30. Results showed that absolute errors of crack width were mostly less than 1.37 mm when the orthogonal distance varied 5.0-7.5 m but significantly increased for greater distances. The orthogonal distance had a disproportionately negative effect compared to the scan angle.