You can let I18n handle pluralization for you, just use count
argument.
You need to set up your locale file like this:
# config/locales/en.yml
en:
online_users:
one: "1 user is online"
other: "%{count} users are online"
And then use the key you just created by passing the count
argument to I18n.t
helper:
I18n.t("online_users", count: 1)
#=> "1 user is online"
I18n.t("online_users", count: 4)
#=> "4 users are online"