How to check my eyesight at home with a snellen chart in my computer? if possible please provide all the lengths in cm?

This will be helpful for you: https://www.hves.com/wp-content/uploads/snellen-chart.pdf View chart at 6 meters, cover one eye, read to the smallest line clearly and record number Repeat with other eye. If the smallest line was read correctly at 3 meters, the visual acuity would be 6/3.

There are some very good apps that you can get to check your vision. Theses are all self explanatory, all eye charts in the US are at 20 feet, the equivalent distance in meters is 6. From this you can easily calculate the centimeters.