How do I work out the right ring band width?

Match the band to the visible width of the finger. As a starting point, a size 4 to 6 finger usually reads best at 1.6 to 2mm. A size 6 to 8 finger sits comfortably at 2 to 2.5mm. A size 8 to 10 finger can carry 2.5 to 3mm without looking dwarfed. The rule of thumb is the band should look like a balanced proportion of the visible finger surface, not a thin line or a wide cuff. Try samples in person before ordering, since the same band width reads differently on a tapering finger than on a uniform one, and digital photos do not capture the in-person scale.

Band width also has to scale with the centre stone. A 0.5ct to 1ct centre sits in proportion on a 1.6 to 2mm band, where a 2.5mm band would visually overpower the stone. A 1ct to 1.5ct centre suits 1.8 to 2.2mm. A 2ct or larger centre needs 2.2mm at minimum, since a thinner band looks structurally underweight under the stone and the ring can read top-heavy from the side. The opposite mismatch is more forgiving: a small centre on a wide band reads as a deliberate design choice in cigar-band styles, while a large centre on a thin band always looks out of proportion.