This is probably the single most common question people have about relationship timing and how long to date before taking a big step, and for good reason: engagement is a huge commitment.
Various relationship surveys and studies over the years have landed on a rough average of somewhere between one and three years of dating before getting engaged, with two years being a commonly cited middle ground. One large survey backs this up almost exactly, finding about 70% of engaged couples had dated two years or longer first, with the engagement itself (proposal to wedding) lasting another 16 months on average, so "two years of dating" is really just the halfway point of the full journey to marriage.
Source: Brite.co
Some couples get there faster, especially if they meet later in life and already know what they want. Others take longer, particularly if there are complicating factors like distance, financial goals, or wanting to finish school or settle into careers first.
What actually matters more than the number of months or years is whether the relationship has been through enough real-life situations to know how you function as a team, how you handle conflict, stress, finances, family dynamics, and boring everyday life. A couple who's dated for 14 months but weathered a lot together can be far more ready than a couple who's dated for three years but has never really been tested.