Secure calculator is the one which works without the necessity of Internet connection.
You can be sure that nobody will get your results only when the computer you work on is not connected to the Internet.
You should permanently delete all of the files containing any of your seed data before connecting your computer to the network.
If you can not calculate the last checksum word by yourself, but you do care about the secureness, you can buy an offline tool
licenced by ledgernano.tips
The tool you will get here is an application working in console mode, tested both on Windows and Linux.
It calculates the last checksum word for any 24-element seed complying BIP39 standard. It implements exactly the same algorithm which works online on this website.
The licence price is 20$
You can pay by one of these 3 cryptocurrency coins - BTC, ETH or ZEC.
To order the application, please contact at:
and let us know which coin you are going to pay.
We accept only cryptocurrency payments.