Two welterweight champions can be seven kilos apart
Division names are not standardised across promotions. Comparing champions without checking the actual limit is close to meaningless.
Welterweight is roughly 75 kg under K-1, 77 under GLORY, and closer to 84 under ONE. So two fighters can hold welterweight titles at the same time, in the same sport, seven or eight kilos apart.
This is not a technicality. It breaks the two things fans do most: comparing champions across promotions, and arguing about pound-for-pound rankings. A fighter dominating at one organisation's welterweight limit may be giving away most of a division to a champion of the same name somewhere else.
It also affects fighters directly. A cut planned for a division name rather than a contracted number is how people miss weight, and the weigh-in timing compounds it — a same-day weigh-in leaves no rehydration window at all, so the cut that was survivable the day before becomes a performance problem.
Our weight class pages compute the spread across organisations for each division, because that disagreement is the useful fact rather than a footnote to it. Bantamweight ranges from 58 kg at K-1 to nearly 66 at ONE, which is not a rounding difference — it is two different sports sharing a word.
The general lesson is the one this site keeps returning to. Kickboxing has no central authority, so nothing is standardised by default: not the rules, not the scoring, and not the divisions.