I'm trying to estimate the block arrival time in etherum PoS.

I was given to understand that every 12 seconds, a new block will be generated. I did a simple calculation but the result is not expected.

E.g. I'm calculating blockIds from 15631000 to 15632000:

# calculating 1000 blocks
15632000 - 15631000 = 1000

# the generated time from etherscan.io
(Sep-28-2022 01:01:23 PM +UTC) - (Sep-28-2022 09:39:59 AM +UTC)

# corresponding epoch time and dividing by 12.
(1664370083 - 1664357999) / 12 = 1007

As you can see, 7 more blocks are missing. But why?

2 Answers 2


There can be instances of Missed blocks. Each slot can be thought of as an opportunity for a block to be produced. In the event that the validator selected for a block production is offline, or fails to successfully propose a block, the slot is considered to be Missed.

See: https://studio.glassnode.com/dashboards/80a0d1ac-d82b-4905-66bb-1ca73c44ff91?&utm_source=cmc_report&utm_medium=cmc_report_01&utm_campaign=cmc_gn_02

  • This is great help, a slot of opportunity is a great idea to understand this.
    – Bai Bing
    Oct 1, 2022 at 6:01
  • 1
    If n block is missed in a slot, next block will have n blockNumber or n+1?
    – MantasFam
    Oct 13, 2022 at 10:06
  • @MantasFam It would still be n. There are no gaps in block numbers, they always increment by 1.
    – eth
    Apr 22, 2023 at 23:53

Proof of Stake added the concept of slots. Slots are every 12 seconds, and usually they are filled with a block. But sometimes the validator/producer for the slot is offline, or their block takes too long to reach the validators that will attest/vote for the block.

So a slot can be empty/skipped (related: Average number of skips for a block). There could be 12, 24, 36 or more... seconds between 2 blocks. There are no gaps in block numbers, they always increment by 1.

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