How is the Bitcoin transaction size calculated?

Question

bitcoin

Here is the transaction dump: take.ms/nNx8j
Here is the transaction on other sites:
https://testnet.smartbit.com.au/tx/2b1c20c84fb8e56...
- here the size is the same as in the dump
https://www. blocktrail.com/tBTC/tx/2b1c20c84fb8e56...
- here the size is absolutely different
https://live.blockcypher.com/btc-testnet/tx/2b1c20...
- and here it is also different, click on Advanced Details
https:/ /testnet.blockexplorer.com/tx/2b1c20c84fb8e...
- here too 152
How do these sites determine transaction size?
Maybe there is a formula unknown to me?
I searched on Google, the search did not return results other than this https://bitcoin.stackexchange.com/questions/1195/h...

Answer 1

Well, how do you define? matches at least one?