how to measure to make it easy!

i’ve noticed that people give sizing numbers like size 8 size 10, but for men buying something for their wife girlfriend or a girl, it is extremely difficult to see if they would fit however, if you take a cloth tape measure and wrap it around yourself, you would get the inches which is far more valuable and easier to get the order and everything right I wish people would be more open-minded and accept this form instead of the traditional hip size or number on the pants