That will depend on the size of the ruler and what it is made out of. A plastic or wooden ruler will be very light, maybe an ounce. A steel ruler will weigh much more.
some people can weigh up to 1,600 pounds some are skinney and may weigh 70 or 60 of course a baby weights 2 to 22 pounds. Perhaps you should have worded it 'How much shoukd I weigh? my age is...and...