Bip39 checksum calculator https://go.bubbl.us/ebe220/f17a?/Bookmarks Even though it utilizes BIP32 technique you could nevertheless import BIP39 seeds into Electrum wallet. Also apart from BIp32 You can find BIP44 Variation which some wallet use with the generation of seeds. For words that only have 3 letters, there's no 4th letter. Such as https://writeablog.net/ipennywpzc/the-ultimate-overview-to-offline-bip39-generators-remain-secure