The word for “heaven” in the Old Testament is the Hebrew word shameh or shamayim, which refers to the sky, the lofty arch above the world where clouds move, and beyond that the place where exist the planets and stars. In the New Testament, the word heaven is a translation of the Greek ouranos, which means “the sky” and “the abode of God” and, by extension, “an eternal realm of happiness and glory.” The sky in its vastness is a metaphor for the vastness and loftiness of God. It is the best earthly representation of the place where God lives.
How big is heaven—how big is the place where God lives? We know that God Himself is infinite. Heaven and earth cannot contain Him. In terms of time, there is no beginning or end to His years (Psalm 102:27); in terms of His kingdom, His reign will have no end (Luke 1:33); in terms of His character, He is unchanging (Hebrews 1:12; James 1:17). God created the heavens and the earth (Genesis 1:1). Of God’s creation of the stars, Isaiah says, “Lift up your eyes on high and see: who created these? He who brings out their host by number, calling them all by name, by the greatness of his might, and because he is strong in power not one is missing” (Isaiah 40:26).
Scientists have not even been able to chart the size of the known physical universe. There is a photo called the XDF (eXtreme Deep Field) that was put together from images taken by the Hubble Space Telescope over the course of ten years. It shows a vast number of galaxies, each comprising billions of stars like our sun. Our sun is 93 million miles away from the earth. And the galaxies are very, very far apart—Andromeda, the closest galaxy to our own, is 2.2 million light years away. To give an idea of how far that is, a shuttle traveling at 18,000 miles per hour would need 37,200 years to travel one light year. The universe is absolutely huge—and God created it all.
So, how big is heaven? We don’t know exactly. The Bible doesn’t give any linear measurements. When John had his vision of heaven, he wrote, “There before me was a great multitude that no one could count, from every nation, tribe, people and language, standing before the throne and before the Lamb” (Revelation 7:9). So heaven is at least big enough for the innumerable multitude—and we can assume that there will be no crowding in heaven.