How to measure girth CORRECTLY???

I really want to know how to measure it correctly,I mean,should I measure only on the widest part?Should I measure only at the base?BTW, what is midshaft?

I want to know it to have an accurate value of penis volume,so anyone please help me with that O.O

Midshaft is the middle of your shaft…so halfway between the base, where your penis enters your body, and the end of your penis. I can only speak for myself, but I measure both base and midshaft. It can’t hurt to keep more specific records. I used a seamstress’s tape with both standard and metric units, and use the metric so there’s no confusion. You can see that I measure both in my sig.

A cloth Taylor’s table works best. I also cut a 3/4 inch strip of paper towel and wrap it around my mid shaft and mark where the front edge meets the rest of the strip. I then lay the strip on a hard ruler and note the place on the ruler where the mark lands. The advantage of using a paper towel strip is that it will not depress into the skin like a string would when pulled tight.

You can use as many points as you like. But surely the biggest, base , midshaft and below the glans.
Most are giving midshaft as measurement to compare isuppose.

Most important for you doing Pe is to be consistent with the way you measure.

My 5.5 in girth came from my widest part,my base is 5.1

should i consider myself a 5.5, 5.1 or a mid term of that (like 5.3)?

You should consider yourself 5.5” at the widest part and 5.1” at the base.
Measure for the sake of tracking your progress, nothing else.