BIP39 Passphrase Generator

Example 1: why a 12-word mnemonic is common

A standard BIP39 mnemonic is derived from entropy plus a checksum. If you start with $128$ bits of entropy:

In this calculator, entropy is entered as hex. Because $1$ hex character is$4$ bits, a 128-bit entropy value corresponds to$128/4 = 32$ hex characters.

Example 2: 24 words from 256-bit entropy

If you use $ENT = 256$ bits (64 hex characters), then$CS = 256/32 = 8$ bits. Total bits:$256 + 8 = 264$, and$264/11 = 24$ words.

Practical takeaway: the “number of words” is determined by the entropy size. If you paste a 24-word mnemonic, this tool derives the matching entropy (if valid for the selected language).

• Prefer longer entropy when you can: $256$ bits yields a$24$-word mnemonic.
• For Japanese mnemonics, spacing rules matter. Copy/paste can introduce non-standard whitespace.
• If you share a link, do not include results unless it’s disposable test data.
• If you need encryption for storing notes, use Encrypt / Decrypt Text rather than inventing a new scheme.

Key relationships

Where $ENT$ is the entropy size in bits, and $CS$ is the checksum size in bits.

Hex input interpretation

In this calculator you enter entropy as a hex string. That corresponds to bits via$\text{bits} = 4 \times \text{hex characters}$. So a 32-hex entropy value is $128$ bits, and a 64-hex entropy value is$256$ bits.

Mnemonic vs seed vs passphrase

• Mnemonic: the word sequence produced by BIP39.
• Seed: a binary value derived from the mnemonic (and optional passphrase) using PBKDF2.
• Passphrase: an optional extra string used with the mnemonic to derive the seed.

Where BIP39 fits

BIP39 covers the mnemonic encoding step. Wallets usually combine it with BIP32 (HD keys) and BIP44 (derivation paths). If your goal is to generate addresses, you’ll need those additional layers.