The average cost of a wedding in the United States is at least $33,000, according to XO Group. That total includes everything from venue costs to food and alcohol, entertainment and the bride's dress.
For that reason, you need to start saving now, says Sethi.
Factoring in the age at which people tend to get married, as well as your own income and ability to save money, you should be able to come up with an idea of how much to start putting aside immediately to finance your dream wedding down the road.
And don't feel like you need to wait until you're engaged, or even in a relationship, to start saving, Sethi says. While some people might feel awkward saving for a wedding so prematurely, Sethi feels the opposite way.
"I think it's weird to not save and to wait until you're 28 [or] 30, and suddenly you say: 'My god, where is this money coming from?'" he says.
Sethi, who is 36, got married in July. He'd actually been saving for his wedding since he was 24 years old, several years before he even met his wife, he tells CNBC Make It.
Long before he was ready to get married, Sethi says, he knew two things for sure: "I knew, one, that I was probably going to get married eventually. Two, I knew that it was going to be a lot more than $30,000, because I'm Indian." (Indian weddings are notoriously extravagant and, even in the US, they cost roughly $65,000 on average, according to one estimate.)
"So, I started saving money every single month in a savings account — I literally called it 'Wedding Savings' — every month I would put money [in] there automatically."
Over the years, Sethi kept putting money into the savings account, while keeping a separate allotment within that account for an engagement ring, he says. When it came time for him to propose to his then-girlfriend, he was able to start budgeting the eventual wedding costs. (Sethi has said previously that you can ignore the old rule of spending two months' salary on an engagement ring. In reality, you should make a budget that makes more sense for you.)