If there are 180 total guests being invited, then the couple may only need 100 to 140 invitations. Always order a few extra invitations in case the couple realizes they forgot to add someone to the list. Also order extra envelopes in case mistakes are made when addressing the invites.
Wedding invitations are one of the biggest parts of wedding planning. It is how guests are informed about a wedding and how the bride keeps track of the guest count. A wedding invitation is also the first look guests get of your wedding.