Large liquid crystal display (LCD) panels have several cell-gap problems. For example, gravity defects are observed as thicker cell-gap areas at the bottom of an LCD panel at a high temperature, and cold-bubble defects are observed as bubbles in an LCD panel at a low temperature. We have developed a gap simulation to investigate these problems. The calculation was carried out for both column and ball spacers. It was shown that gap defects can be substantially reduced using ball spacers.