An online calculator is a useful tool for checking your work, especially when you work with crypto and hashes.
The following sites DO NOT implement SHA-3 correctly. In other words they do NOT generate the FIPS test vectors.
https://dl.dropboxusercontent.com/u/186 ... index.html
https://leventozturk.com/engineering/sha3/
http://www.calczilla.com/math/secure-hash/
http://www.freecodeformat.com/sha3.php
https://www.rajiv.com/blog/2013/08/21/sha-3-hash/
http://toolsr.com/hash-generator#hash
http://www.fishtrap.co.uk/online-sha3/# (site is broken, doesn't compute hashes at all)
The code in my GitHub generates the CORRECT, published, test vector results. These sites DO NOT, and therefore SHOULD NOT BE USED!
Some of these sites seem to be based on early implementations of SHA-3, which has undergone work since then, eventually becoming a FIPS, published standard.
Sites that generate CORRECT hashes
http://emn178.github.io/online-tools/sha3_256.html (Unfortunately can only hash text)