EUI-64 Calculator
Convert a 48-bit MAC address into its modified EUI-64 interface identifier and the resulting IPv6 address.
About EUI-64 Calculator
Modified EUI-64 splits the MAC in half, inserts ff:fe in the middle and flips the universal/local bit so that a globally unique MAC produces an identifier marked as universally administered. This is the identifier SLAAC generates by default, so being able to derive it by hand is how you predict an address before a host boots and how you recognise one in a log.
Formula
EUI-64
ff:fe is inserted between the OUI and the device identifier, and bit 7 of the first octet (the universal/local bit) is inverted.
- OUI
- First 24 bits of the MAC, identifying the vendor
- ff:fe
- Fixed padding that stretches 48 bits to 64
Worked example
With the default values below, EUI-64 Calculator returns EUI-64 Interface ID of 021a:2bff:fe3c:4d5e. Change any input above and every figure here is recalculated in your browser.
Inputs used
- MAC address
- 00:1a:2b:3c:4d:5e
- Network prefix (first four groups)
- 2001:db8:acad:1
Results
- EUI-64 Interface ID
- 021a:2bff:fe3c:4d5e
- Resulting IPv6 Address
- 2001:db8:acad:1:21a:2bff:fe3c:4d5e
- Universal/Local Bit Flipped To
- 1 (universal)
- Vendor OUI
- 00:1a:2b
Step by step
- 1Values used
- 2EUI-64
- 3EUI-64 Interface ID= 021a:2bff:fe3c:4d5e
- 4Resulting IPv6 Address= 2001:db8:acad:1:21a:2bff:fe3c:4d5e
- 5Universal/Local Bit Flipped To= 1 (universal)
- 6Vendor OUI= 00:1a:2b
Assumptions and limits
- The result is derived only from the 2 inputs listed above. Anything not among them is not part of the calculation.
- In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.
Frequently Asked Questions
How is EUI-64 calculated?
ff:fe is inserted between the OUI and the device identifier, and bit 7 of the first octet (the universal/local bit) is inverted. Modified EUI-64 splits the MAC in half, inserts ff:fe in the middle and flips the universal/local bit so that a globally unique MAC produces an identifier marked as universally administered.
Why does EUI-64 matter?
This is the identifier SLAAC generates by default, so being able to derive it by hand is how you predict an address before a host boots and how you recognise one in a log.
What values do I need to enter?
This calculator takes 2 inputs: MAC address, Network prefix (first four groups). The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.