We don’t know the "exact" number of how old the universe is.

However, at present, after theorizing it through different methods, scientists believe that the universe is 13.82 billion years old.

Till date, the people working on it has come up with two methods to determine the age of our universe.

How old is the Universe 2019? (Courtesy: Just Science)

The first one includes studying the oldest objects within the universe. Once we know what's the old star, we can trace back its existence. A universe, after all, can’t be older than its oldest object.

The second one includes measuring the expansion rate of the universe and then tracking it backward to get to the inception point.

Of course, both these measures have massive challenges on way.

For instance, identifying the oldest star and/or globular clusters (which is a collection of stars) in the universe and then determining its age, which depends on a very diverse range of factors including its mass and brightness, isn’t easy.

cosmic (Courtesy: Universe Today)

Similarly, determining the expanse of the universe and tracing it back through all the cosmic events it went through over billions of years, it is difficult.

However, the likes of Planck (European Space Agency's spacecraft) and NASA's Wilkinson Microwave Anisotropy Probe (WMAP), with the help of Spitzer Space Telescope, has helped us establish that our universe is 13.82 billion years old.

Of course, this number can be wrong. After all, only a few years back, we thought that the age of the universe is 18 billion years.

universe (Courtesy: YouTube)

But, conclusively, to answer your question - how old is the universe - it is 13.82 billion years old.