I have had measurements done in a dress shop and was told what size my bust was and have been using that. I weighed less then when the measurements were done than I do now. They taught me how to get an exact measurement and I have been using that. I ordered this bra according to that method (after ordering other bras with the same method and getting perfect fits) and the bra runs a bit large at the top of the bust. Everything else fits fine and the straps are comfortable on my shoulders. The only major downside to the straps is they are not adjustable. I could have compensated for the big fit at the top of the bust if the straps would have been adjustable.