There are approximately 700,000 blocks as of March 2021 [1]. How comes the blockchain size is only ~350 GB [2] and not 700 GB given that the block size is 1 MB?

Thank you for your help.

  • The block size is not 1MB, It is 4 weight units (which can be comprised of up to about 4MB of data). This change came into effect in 2017, so the upper bound of the possible blockchain size is actually larger than OP suggests.
    – chytrik
    Apr 21, 2021 at 21:37

1 Answer 1


1 MB was the maximum Bitcoin block size until 2017, not the size of each block. In the early years there were few transactions and most blocks were almost empty.

After the august 2017 segwit soft fork, the way how the transactions size are measured and the maximum space available has changed, now blocks can be bigger than 1 MB. If you are interested, you can find here how the things works now: https://en.bitcoin.it/wiki/Weight_units

This is the historical chart of Bitcoin average block size

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currently the average block size is about 1.33 MB

Edit: I have updated my answer to take into account the changes introduced with segwit soft fork.

  • 1 MB is the maximum size of what?
    – user103136
    Apr 21, 2021 at 13:40
  • I corrected the answer, thanks Apr 21, 2021 at 14:45
  • 2
    Maximum blocksize for Bitcoin is not 1 MB anymore since Segwit was activated (2017): bitcoin.stackexchange.com/a/98811
    – user103136
    Apr 21, 2021 at 15:14
  • modified, I hope it goes well now :) Apr 21, 2021 at 22:18

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