It is too big.
'Grande' — GRAN-de. Two clear syllables.
Say this in the fitting room when the item does not fit and you need a smaller size. Follow immediately with 'avete una taglia più piccola?' to continue the process smoothly.
'Troppo' means too (as in too much/big/small). 'Grande' means big or large. The phrase is complete as is — no subject needed in Italian. For specific fit issues: 'è troppo largo' (too wide), 'è troppo lungo' (too long), 'è troppo stretto' (too tight).
È un po' grande.
It is a little big.
Softer — minor size issue.
Mi nuota addosso.
It swims on me.
Idiomatic — the garment is way too big.
Avete una taglia più piccola?
Do you have a size smaller?
The natural follow-up.
Italians use the verb 'cadere' (to fall) to describe clothes that are too big: 'mi cade' (it falls on me). This vivid language is part of everyday Italian fashion vocabulary even in casual conversation.