In Buddhism there are four different lengths of kalpas. A regular kalpa is approximately 16 million years long, and a small kalpa is 1000 regular kalpas, or 16 billion years. Further, a medium kalpa is 320 billion years, the equivalent of 20 small kalpas. A great kalpa is 4 medium kalpas, or 1.28 trillion years.
The Buddha had not spoken about the exact length of the kalpa in number of years. However, he had given several astounding analogies to understand it.
1. Imagine a huge empty cube at the beginning of a kalpa, approximately 16 miles in each side. Once every 100 years, you insert a tiny mustard seed into the cube. According to the Buddha, the huge cube will be filled even before the kalpa ends.
2. Imagine a gigantic rocky mountain at the beginning of kalpa, approximately 16 x 16 x 16 miles (dwarfs the Everest!). You take a small piece of cloth and wipe the mountain once every 100 years. According to the Buddha, the mountain will be completely depleted even before the kalpa ends.
In one situation, some monks wanted to know how many kalpas had passed away so far. The buddha gave the analogy:
1. If you count the total number of sand particles at the depths of the Ganges river, from where it begins to where it ends at the sea, even that number will be less than the number of passed kalpas.