Overview
Introduction
NTLM is the password hash format Windows has used internally since Windows NT: a single MD4 pass over your password's UTF-16LE bytes, with no salt and no work factor.
This tool computes that same NTLM hash for any text you provide, entirely in your browser, useful for authentication research, reproducing a known value, or legacy Windows interoperability work.
What Is NTLM Hash Calculator?
The NTLM hash (sometimes called the NT hash) is MD4(UTF-16LE(password)), producing a 128-bit digest shown here as 32 hexadecimal characters, identical in size and format to a plain MD4 or MD5 digest.
It's distinct from the NTLM authentication protocol itself (the challenge-response exchange used to prove knowledge of a password over a network); this tool computes the underlying stored password hash, the building block that protocol relies on.
How NTLM Hash Calculator Works
Your input text is first encoded as UTF-16LE (each character becomes two bytes, low byte first), rather than the UTF-8 encoding every other tool in this category uses.
Those UTF-16LE bytes are then run through the unmodified MD4 algorithm (RFC 1320), producing the same 128-bit digest structure as this category's standalone MD4 tool, just over a different byte encoding of the input.
When To Use NTLM Hash Calculator
Use this when researching Windows authentication internals, reproducing a known NTLM hash for a security assessment you're authorized to perform, or debugging legacy software that stores or compares NTLM hashes directly.
Never use NTLM as a password-hashing scheme in anything you design yourself; it has no salt and no work factor, so a leaked table of NTLM hashes is trivially crackable with modern hardware.
Often used alongside MD4 Hash Calculator, MD5 Hash Calculator and Random NTLM Hash Generator.
Features
Advantages
- Extremely fast to compute, since it's just a single unmodified MD4 pass.
- Well-documented, stable format that hasn't changed since Windows NT.
- Useful for reproducing exact values when studying or auditing Windows authentication behavior.
Limitations
- No salting: identical passwords always produce identical hashes, making precomputed rainbow-table attacks effective.
- No configurable work factor, unlike bcrypt, scrypt, or Argon2; a modern GPU can attempt billions of NTLM guesses per second.
- Inherits MD4's cryptographic weaknesses, though NTLM's practical exposure comes mainly from the lack of salting and slow-hashing, not MD4 collisions specifically.
Examples
Best Practices & Notes
Best Practices
- Only use this tool for research, authorized security assessments, or legacy interoperability, never as a password-storage scheme for anything you build.
- If you're designing new password storage, use a dedicated slow hash like bcrypt, scrypt, or Argon2, not NTLM, MD4, or MD5.
- Remember NTLM hashes UTF-16LE bytes, not UTF-8; comparing against a UTF-8-based MD4 tool on the same input will not match for non-ASCII text.
Developer Notes
This tool re-uses this category's existing pure-TypeScript MD4 implementation (RFC 1320), the only change is encoding the input as UTF-16LE instead of UTF-8 before hashing, matching the MS-NLMP specification's NT hash construction. Verified against the widely published NTLM("password") test vector and against plain MD4's known empty-string digest.
NTLM Hash Calculator Use Cases
- Reproducing a known NTLM hash while studying Windows authentication internals
- Verifying NTLM hash values during an authorized penetration test or security assessment
- Debugging legacy software that stores or compares NTLM password hashes directly
- Cross-checking a value against other Windows authentication tooling
Common Mistakes
- Assuming NTLM hashes are salted like a modern password hash; they are not, and identical passwords always produce identical hashes.
- Comparing an NTLM hash against a UTF-8-based MD4 or MD5 digest of the same text and expecting a match for non-ASCII input, since the byte encoding differs.
- Using NTLM (or building anything similar) as a real password-storage scheme in new software.
Tips
- If your value doesn't match another tool's output, check whether that tool is hashing UTF-8 bytes instead of UTF-16LE, that's the single most common source of NTLM mismatches.
- Use the plain MD4 tool alongside this one on the same ASCII-only input to see how the choice of UTF-16LE vs UTF-8 encoding changes the resulting digest.