Our walk-in closet is ~15.8 m^2 (~170 square feet).
I have a gun safe, and maybe 8 feet of clothes rod, plus maybe 6 linear feet of shelf with shoes (we have a 6 foot wide shelf around 7 feet tall with shelves every 6-8 inches—my shoes get the 6 foot wide top row (that she cannot reach)). My wife, OTOH has the entire rest of that shelf filled with shoes. I think she has more shoes in that shoe shelf than I've had shoes, period, in my life.
My 8 feet of clothes rod in the closet (loosely packed) comp[ares to her 38 feet of rod packed rather tightly. Then she has shelves with baskets of folded stuff. This is all in addition to dresser drawers that are not in the closet, lol.