Subnet for 75 hosts
A network that needs 75 hosts fits in a /25, mask 255.255.255.128, with 126 usable addresses.
A network built for 75 hosts needs a /25. The mask is 255.255.255.128, and its 126 usable addresses leave 51 spare for growth.
The next smaller block, a /26, only allows 62 usable addresses, which is not enough for 75 hosts. That makes /25 the smallest block that fits.
Enter any address below to see the exact network, broadcast, and host range for a /25 block.
Calculate a /25 network
Accepts CIDR (192.0.2.0/24), IP + mask (192.0.2.0 255.255.255.0), or a bare IP (defaults to /24).
11000000.00000000.00000010.0000000011111111.11111111.11111111.10000000Example: 192.0.2.0/25
Taking 192.0.2.0/25 as a worked example, a /25 block breaks down like this:
| Network address | 192.0.2.0 |
|---|---|
| Usable range | 192.0.2.1 - 192.0.2.126 |
| Broadcast address | 192.0.2.127 |
| Total addresses | 128 |
| Usable hosts | 126 |
Frequently asked questions
What subnet mask do I need for 75 hosts?
A network with 75 hosts fits in a /25, which uses the mask 255.255.255.128 and provides 126 usable addresses.
How many addresses does a /25 block have in total?
A /25 has 128 total addresses, 126 of them usable (the total minus the network and broadcast addresses, except for /31 and /32).
Does a /25 waste any addresses for 75 hosts?
Yes, 51 addresses of headroom. A /25 provides 126 usable addresses for the 75 you need, and the next smaller block, a /26, does not hold enough.
How do I work this out myself?
Find the smallest power of two, minus two, that is at least 75. That takes 7 host bits, which leaves a /25 prefix. See how to calculate a subnet mask for the full method.