I assume you want to measure it. Several methods come to mind:
Trigonometry. Find a spot where you can stand that the top of the building is exactly 45 degrees above your horizontal sight line. Then, measure the horizontal distance with a tape, or by stepping it off.
Gravity. Drop a heavy weight from the top (heavy enough that its OK to ignore air resistance). Time the fall, and do the math.
Estimates. Count the floors, and estimate a height of each. Or, count wall panels. Count steel sets inside the elevator shafts. Steps on the stairways. Many different estimates.
There’s definitely other ways to do this, but these came to mind first.