Konoha was founded during the warring clan era by Hashirama and Madara. Now, to have the power and get acknowledged by the other clans to create Konoha, they have to have been somewhere between age 25 to 35. Hashirama's brother, the 2nd Hokage, would have been around the same age too.

In a flashback, we can see that the 2nd Hokage was just around 30 years old when he was killed by the Gold and Silver brothers. 

And the 3rd Hokage has been his disciple since being a genin. From this, we can say that Konoha was created just around the same time as when the 3rd hokage was born. 

And he was 68, I think, when he was killed by the Snake sennin. Add another 30 years when Boruto takes place.

In short:

- Add some 5 years for the 1st Hokage's term.
- Add another 5 years for 2nd Hokage's term.
- Add around 55 years for 3rd Hokage's term.
- And another 5 years for 4th Hokage's term.
- (Start of canon) add 13 years till Naruto is gennin
- Then add 3 years for the time skip
- (*Naruto Shippuden* starts) Then add 30 years for the skip to when Boruto takes place.

So totally Konoha is around 110 years old.