Simple approximate solutions of internal circulation periods (t(c)) of liquid in falling droplets for low Reynolds number (N-Re), which are needed for describing the effect of internal circulation of liquid in droplets on the gas absorption rate of liquid drops, were obtained. A simple solution of t(c) for the liquid in the differential shell region near the inside surface of a droplet, denoted as t(cs), was first analytically derived in terms of xi, where xi is the stream function describing the flow motion in the liquid drop. The values of t(cs) (Eq. (19)) agree with those of Kronig and Brink (1950) with relative errors less than 3.6 and 6 % for xi less than or equal to 0.1 and 0.2, respectively. Thus, the theoretical solution of Eq. (19) is valid for xi less than or equal to 0.2. The obtained t(cs) was further modified by simple correlation to extend its applicability to the full range of xi (0 less than or equal to xi less than or equal to 1). The relative errors of the modified solutions for the full xi, denoted as t(cf), were less than 1.1 % for xi greater than or equal to 0.01. A simple correlation equation based on the theoretical values of Kronig and Brink (1950) was also made. The relative errors of this correlation equation were less than 3.7 % for 10(-6)less than or equal to xi less than or equal to 1. The solutions of this analysis avoid the complexity of the elliptic integral terms encountered in that of Kronig and Brink (1950) and thus are much easier to apply and may help in engineering design or estimation. With the simple solutions, one can easily note that t(c) increases twice and 3.9 times as xi decreases from xi =1 to about 1/117.5 and 10(-6), respectively.