I bring a tape measure, even clothing from the same brand can be different sizes.

Women have this issue in most stores. Each brand determines what is a "size two" differently.

Different cuts

I feel your pain. Years ago I learned to ALWAYS try clothing on before buying it. Especially if the stuff was made in a different country, like China, then the sizes are going to be all screwed up.

The world of 'fashion' rarely standardizes sizes - despite some of the regulations of the industry. If they have sizes which do not sell so easily as others, the tag is often altered.

Had this problem loads of times, its called a rip off!