Finite size effects on classical ideal gas are revisited. The micro-canonical partition function for
a collection of ideal particles confined in a box is evaluated using Euler?Maclaurin?s as well as
Poisson’s summation formula. In Poisson’s summation formula there are some exponential terms which
are absent in Euler?Maclaurin?s formula. In the thermodynamic limit the exponential correction is
negligibly small but in the macro/nano dimensions and at low temperatures they may have a great
significance. The consequences of finite size effects have been illustrated by redoing the
calculations in one and three dimensions keeping the exponential corrections. Global and local
thermodynamic properties, diffusion driven by the finite size effect, and effect on speed of sound
have been discussed. Thermo-size effects, similar to thermoelectric effects, have been described in
detail and may be a theoretical basis with which to design nano-scaled devices. This paper can also
be very helpful f…