Let's face it, bringing up the topic can be pretty damn awkward, so a lot of couples choose to avoid the conversation all together.
Like the men and women in this video by Elite Daily.
Some of them have been together for years, some for months. But none of them have any idea what their partner's "magic number" is.
"We're happy, we don't have to know this," one woman says.
Ahh, if only everyone in the video had chosen to opt out....