<p>The checksum is 1 bit for every 3 words so 1/16 for 12 words, 1/64 for 18 words and 1/256 for 24 words</p>

CC BY-SA 4.0
2021-08-09T09:56:00.170Z
2021-08-09T09:56:00.170Z
Mike D
<p>from <a href="https://github.com/bitcoin/bips/blob/master/bip-0039.mediawiki" rel="nofollow noreferrer">https://github.com/bitcoin/bips/blob/master/bip-0039.mediawiki</a>:</p>
<blockquote>
<p>The following table describes the relation between the initial entropy length (ENT), the checksum length (CS), and the length of the
generated mnemonic sentence (MS) in words.</p>
</blockquote>
<pre><code> CS = ENT / 32 MS = (ENT + CS) / 11
 
|  ENT  | CS | ENT+CS |  MS  |
+-------+----+--------+------+ 
|  128  |  4 |   132  |  12  |
|  160  |  5 |   165  |  15  | 
|  192  |  6 |   198  |  18  | 
|  224  |  7 |   231  |  21  | 
|  256  |  8 |   264  |  24  |
</code></pre>
<p>so for 12, 18, 24 words, the entropy of the checksum is 4, 6, 8</p>
<p>or 1 in 16, 64, 256</p>

CC BY-SA 4.0
2021-08-09T14:04:10.347Z
2023-04-03T14:23:50.440Z
2023-04-03T14:23:50.440Z
hedgedandlevered
<p>Any private key in existence, I am guessing a few million created by now, in 2<sup>256</sup>, are your chances of guessing someones mnemonic/private key. 2<sup>256</sup> is a very, very large number.</p>

CC BY-SA 4.0
2021-07-10T08:18:16.403Z
2021-07-10T08:23:36.853Z
2021-07-10T08:23:36.853Z
stackaccount
<p>If you mean &quot;valid&quot; being the valid checksum word at the end of the phrase,
A valid mnemonic is defined as:</p>
<blockquote>
<p>The checksum is then the first n / 32 bits of the SHA256 hash of the entropy. This is just concatenated to the end of the entropy. The mnemonic is then encoded by dividing the entropy into groups of 11 bits and using the resulting 11 bit number as an index into a list of 2048 words</p>
</blockquote>
<p>So I would think getting a valid checksum for any arbitrary input would be 1/2048</p>

CC BY-SA 4.0
2021-02-10T07:06:52.123Z
For 12 words (128 bits) 128/32=4 bits = 1/16; for 18 words (192 bits) 1/64; for 24 words (256 bits) 1/256. The checksum is never 11 bits. (Also: pneumonic means relating to the lungs, or breathing; mnemonic relates to memory.)
dave_thompson_085
CC BY-SA 4.0
2021-02-09T21:48:42.630Z
2024-02-26T13:49:35.913Z
2024-02-26T13:49:35.913Z
8vtwo
<p>So, here is the statement: &quot;Not every combination of words from bip39 wordlist is valid.&quot;</p>
<p>What are the chances of hitting a VALID mnemonic phrase out of bip39, if someone picks 12, 18 and 24 words from the word list randomly by himself?</p>

CC BY-SA 4.0
2021-02-09T16:34:34.530Z
Hi crypto enthusiast, interesting question. It might help if you add a source for the statement so that answerers can investigate the context in which it was made.
Murch
CC BY-SA 4.0
2021-02-09T21:45:43.457Z
This question does not need any more context.
8vtwo
<mnemonic-seed>
What are the chances of hitting VALID mnemonic phrase out of bip39, if someone picks 12, 18, or 24 words from the word list randomly by himself?
crypto enthusiast
# What are the chances of hitting VALID mnemonic phrase out of bip39, if someone picks 12, 18, or 24 words from the word list randomly by himself?

(Asked by: username_0 on 2021-02-09)

So, here is the statement: "Not every combination of words from bip39 wordlist is valid."

What are the chances of hitting a VALID mnemonic phrase out of bip39, if someone picks 12, 18 and 24 words from the word list randomly by himself?

**Tags:** mnemonic-seed

> **Comments:**
> **username_1**: Hi username_0 username_0, interesting question. It might help if you add a source for the statement so that answerers can investigate the context in which it was made.  
> **username_2**: This question does not need any more context.  

---

## 4 answers

### Answer by username_3 on 2021-08-09. Score: 1

The checksum is 1 bit for every 3 words so 1/16 for 12 words, 1/64 for 18 words and 1/256 for 24 words


---

### Answer by username_4 on 2021-08-09. Score: 0

from <https://github.com/bitcoin/bips/blob/master/bip-0039.mediawiki>:

> The following table describes the relation between the initial entropy length (ENT), the checksum length (CS), and the length of the
> generated mnemonic sentence (MS) in words.

```
 CS = ENT / 32 MS = (ENT + CS) / 11
 
|  ENT  | CS | ENT+CS |  MS  |
+-------+----+--------+------+ 
|  128  |  4 |   132  |  12  |
|  160  |  5 |   165  |  15  | 
|  192  |  6 |   198  |  18  | 
|  224  |  7 |   231  |  21  | 
|  256  |  8 |   264  |  24  |

```

so for 12, 18, 24 words, the entropy of the checksum is 4, 6, 8

or 1 in 16, 64, 256


---

### Answer by username_5 on 2021-07-10. Score: 0

Any private key in existence, I am guessing a few million created by now, in 2256, are your chances of guessing someones mnemonic/private key. 2256 is a very, very large number.


---

### Answer by username_2 on 2021-02-09. Score: 0

If you mean "valid" being the valid checksum word at the end of the phrase,
A valid mnemonic is defined as:

> The checksum is then the first n / 32 bits of the SHA256 hash of the entropy. This is just concatenated to the end of the entropy. The mnemonic is then encoded by dividing the entropy into groups of 11 bits and using the resulting 11 bit number as an index into a list of 2048 words

So I would think getting a valid checksum for any arbitrary input would be 1/2048

> **Comments:**
> **username_6**: For 12 words (128 bits) 128/32=4 bits = 1/16; for 18 words (192 bits) 1/64; for 24 words (256 bits) 1/256. The checksum is never 11 bits. (Also: pneumonic means relating to the lungs, or breathing; mnemonic relates to memory.)  

---

