Stop using printable ring sizers. They distort the finger, the paper stretches, and the result is usually a half-size off. The jeweller method we use in the studio is the only one we trust at home: a strip of soft plastic, pulled snug, marked where it meets, then measured.
Measure at the end of the day, not the morning. Fingers swell through the day; a morning measurement will be a half-size small by evening. Measure three times across three days and take the median — your size is not a single number, it is a small range.
If you are choosing between two sizes, size up. A slightly loose ring can be fitted with a sizing bead; a tight ring has to be cut and re-soldered, and the cut leaves a faint mark inside the band.