The honest test
Without it, health, housing, work or legal standing suffers within the month: rent, basic groceries, utilities, transport to work, medicine, insurance, minimum debt payments.
Everything that upgrades a need or adds pleasure: restaurants, streaming, newer car than needed, brand preferences, hobbies. Wants are not sins — they're the reward lane, sized on purpose.
Ask 'is there a cheaper version that does the same job?' The gap between the version you have and the cheapest workable version is want-spending inside a need.

Where people argue with themselves
Getting to work: need. The $560/month model when a $290 one drives the same route: $270 of want.
A working phone: need (and a job-search tool). The flagship upgrade every year: want.
Groceries: need. Restaurants and delivery: want — budgeted happily, counted honestly.
Health and skills spending can be a genuine need. The test is function, not fun — some of the best money you'll spend is here.