If you are not ordering a bentwood ring or a deer antler ring, then more likely getting sized at a jewelry store is completely fine.
Getting your finger sized at a local jeweler is always a good idea. However, it is not always a 100% guarantee. Jewelers can take measurements in different ways. Some measure using comfort fit, standard fit, European sizing, etc. One of the best ways to confirm your size is by using our free ring sizer.
Link To Free Ring Sizer
https://northernroyal.com/products/ring-finger-size-measuring-gauge-tool-ring-sizing-tool-for-measuring-finger