First of all, regarding the barrel diameter, it is suggested to sit on the ground and measure the distance from the buttocks to the toes as a reference for the barrel diameter, but add 30 cm as a possible activity space when taking a bath, because it is impossible for people to stick their buttocks to the back wall and their soles to the front wall. It is best not to tilt their legs because the barrel diameter is too small and feel uncomfortable for a long time.

Regarding the barrel height, it is suggested to sit on the ground and measure the distance from the hip to the neck as a reference for the barrel height, which can be slightly increased by 5 cm as the barrel height. Because the water can't be too full, so as to avoid people overflowing into the water, which is not conducive to health maintenance. However, the height should not be too low to avoid soaking in the shoulders when there is not enough water. The upper edge of the bucket should also take care of people's sight when taking a bath, and it should not be too high to block the sight.

Finally, if the barrel needs two people to bathe together, the diameter should be based on the tall one and the height should be based on the short one to avoid drowning. Because warm baths sometimes make people dizzy.

I hope this answer is helpful to you.