Each input adds 180 bytes to the transaction.
Each output adds 34 bytes to the transaction.
There is a fixed 10 bytes per transaction.
Transaction size = 180 bytes per input + 34 bytes per output + 10 bytes
This transaction has a size of 224 bytes, https://blockchain.info/tx/4c1ad203e13a0b185fa870e751879f127307d08f67e30508a4682537ad64d05a
1*180 + 1*34 +10 = 224
A typical transaction is around 500 bytes.
Each output adds 34 bytes to the transaction.
There is a fixed 10 bytes per transaction.
Transaction size = 180 bytes per input + 34 bytes per output + 10 bytes
This transaction has a size of 224 bytes, https://blockchain.info/tx/4c1ad203e13a0b185fa870e751879f127307d08f67e30508a4682537ad64d05a
1*180 + 1*34 +10 = 224
A typical transaction is around 500 bytes.
your tx example has 2 outputs which means your calculation should be like this:
1*180 + 2*34 +10 = 258
the reason why you are getting a wrong number is that you read the "old description" of how to calculate transaction size not the new one.
the 180 is for uncompressed keys, these days (like your example key) all keys are compressed and 180 should be 148 instead
