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 flash back 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 and when boruto takes place.

So add some 5 years for the 1st hokages term.
Add another 5 years for 2nd hokages term.
Add around 55years for 3rd hokages term.
And another 5 years for 4th hokages term.
(Start of cannon)
Add 13 years till naruto is gennin
Then add three 3 years for the time skip
(Naruto Shippuden)
Then add 30 years for skip to when boruto takes place.

So totally konoha is around 110 years old.