Gas adsorption in carbon nanotubes is an interesting issue as it affects both the electrical and chemical properties of nanotubes. This effect can be exploited for designing different types of nanosensors. In this paper, chiral carbon nanotubes of different diameters and chiral angle have been considered to investigate the effect of chirality on the sensing capability of single walled carbon nanotubes. Here, the adsorption binding energy of ammonia has been estimated in each tube of varying dimension. The electrical conductivity change and sensitivity of nanotube due to ammonia adsorption has also been calculated. The results are compared with that of achiral tubes of same size. Based on the observations, it has been concluded that (8,3) chiral carbon nanotube is more suitable for ammonia sensor application.