Free tool

MAC address block capacity calculator

How many devices does an IEEE MA-L, MA-M or MA-S assignment actually cover? Enter your production numbers and get the address capacity, the devices supported at however many MAC addresses each unit needs, and an estimated exhaustion date.

MA-L

16,777,216 EUI-48 addresses in the assignment

16,777,216 Addresses available with no reserved safety margin

16,777,216 Devices supported at 1 MAC address each

Impact of multiple MAC addresses per device

MAC addresses per device	Devices supported
1	16,777,216
2	8,388,608
3	5,592,405
4	4,194,304

MA-L, MA-M and MA-S capacities

The IEEE Registration Authority issues three sizes of assignment. The number in the name is how many bits of the 48-bit address the assignment fixes; the rest are yours to allocate to devices.

Assignment	Assigned bits	Device bits	EUI-48 addresses
MA-L	24	24	2²⁴ = 16,777,216
MA-M	28	20	2²⁰ = 1,048,576
MA-S	36	12	2¹² = 4,096

An MA-L assignment is what most people mean by an OUI: the full 24-bit organizationally unique identifier is yours and nobody else's. An MA-M or MA-S holder shares those first 24 bits with other organizations and is assigned a longer prefix, so a vendor lookup has to match the complete assigned prefix rather than just the OUI. See how MAC addresses are structured for the bit layout. An MA-S is only 4,096 addresses; at two interfaces per unit that is 2,048 devices before any margin.

This tool does not issue or register assignments, and macadress.com is not affiliated with IEEE. To apply for an assignment, see the IEEE Registration Authority.

Once you hold a block

Allocating within it, without duplicates and across multiple factories, is its own job. See how to allocate MAC addresses during manufacturing and MAC address pool management for multiple factories, or run the allocation with MAC address allocation on the Scale plan. Just need throwaway addresses for a test fixture rather than a real assignment? The random MAC address generator runs entirely in your browser.