This thread has become amusing. Not many familiar with precision measurement. In a machine shop, the least accurate way to measure something is with the most precise ruler that you can buy - a thin steel rule, with .010 inch increments, but for some jobs, it's good enough.
You don't even need to read the markings, when measuring a chain, since it's precisely 12 inches long. Just lay one end on the edge of a pin and see how much of the pin at the opposite end is exposed. If it's less than half, the elongation is still under .5%. The rule is made thin, so the markings that most people need to use can be placed close to the item being measured, to minimize error. Tape measures are worthless.
Here's an adequate rule that's cheap:
https://www.amazon.com/General-Tools.../dp/B00004T7SR