Since the Bible was written in ancient Hebrew and Aramaic, translations vary greatly, and so there is no single count for the occurrence of the word "heaven." Rather, its appearance differs according to which translation is used.
The King James version of the Bible mentions the word "heaven" 327 times in the Old Testament and 255 times in the New Testament. Meanwhile, the word appears only 186 times in the New International Version's Old Testament and 236 times in its New Testament. In the New Revised Standard Version, "heaven" appears 246 times in the Old Testament and 248 times in the New Testament.