Seed phrase strength calculator
How many possible 12 or 24-word seed phrases are there, and how long would it take to guess one? Pick the number of words to see. It never asks for your words. Free, no sign-up, nothing leaves your browser.
For phrases made at random by a wallet using the BIP39 standard. A phrase someone chose themselves, or one with words left out, can be far weaker. Never type your real seed phrase into any website.
Where the strength comes from
Most wallets follow a standard called BIP39, which picks each word from a fixed list of 2,048. A 12-word phrase holds 128 bits of randomness and a 24-word phrase 256 bits; the last word also carries a small checksum that catches typing mistakes. Every extra bit doubles the number of possible phrases.
Why guessing doesn't work, and what does
Even at speeds far beyond any real computer, guessing a randomly generated 12-word phrase would take vastly longer than the age of the universe. That is why thieves don't guess seed phrases: they trick people into typing them into fake websites or apps, or find them stored in photos, emails or cloud notes. Never enter your real seed phrase anywhere, including this page, which doesn't ask for it.
Run your own crypto app
With a custodial service, the provider holds the keys for you and there's usually no seed phrase to manage. SendPay crypto platforms let your customers buy, sell and hold crypto, with assets held with regulated partners.