Is it normal to check out other girls while in a relationship?
Mostly.Normal for most people
Yes, it’s normal to notice or find other people attractive while you’re in a relationship. Whether “checking them out” is a problem depends on how you do it and what boundaries you and your partner have agreed on.
Being in a relationship doesn’t switch off your ability to notice attractive people. A quick glance or private thought is pretty ordinary; it doesn’t automatically mean you’re unhappy or planning to cheat.
There’s a difference between noticing someone and making your partner feel ignored, openly ogling someone, or turning it into flirting. People draw that line differently, so talk about it if it’s bothering either of you—and try to agree on boundaries that feel respectful to both.