For our column “What I Can’t Live Without,” we’ve interviewed hundreds of famous people about their favorite products — here, we’re going deep into their favorite T-shirts. If you ...

Our wardrobe-basics writer asked some stylish guys about their favorite black T-shirts, tested a few, and found the best black T-shirt overall: the Buck Mason slub.

The largest sizes of those T-shirts, XL, roughly equates to a size 10. “Flore Flore is a bit fitted, but women, mothers, grandmas, all different body types wear it,” Ms. van Zuilen said.

Style experts recommend the best white T-shirts for women that they wear and love from Leset, Uniqlo, J.Crew, Aritzia, and more.