IP Subnet Calculator

Address plus mask into network, broadcast, usable range and host count.

What you provide

Any address in the block. A pasted 10.0.0.0/8 works too.

Prefix length or dotted-quad mask — either is accepted.

Result

192.168.1.0/24 — 254 usable hosts

192.168.1.10 is a host inside this block, not the block itself. The subnet starts at 192.168.1.0 and ends at 192.168.1.255, with the first and last reserved for the network and broadcast addresses.

32 bits, split at /24

Address

11000000101010000000000100001010

192.168.1.10

Mask

11111111111111111111111100000000

255.255.255.0 — /24

Network

11000000101010000000000100000000

192.168.1.0/24

  • Network — 24 bits, fixed
  • Host — 8 bits, free to vary
Diagnostic telemetry
Network address
192.168.1.0/24
Subnet mask
255.255.255.0
Wildcard maskThe inverse — what ACLs and OSPF take
0.0.0.255
Broadcast address
192.168.1.255
Usable host range
192.168.1.1 – 192.168.1.254
Usable hosts
254
Total addresses
256
Scope
Private (RFC 1918)
Historic classClassful addressing ended in 1993 — shown because exams still ask
C
Splits into /25
2 subnets of 126 hosts

What this cannot tell you

  • Pure arithmetic on the address and mask you enter. It does not query any network, so it cannot tell you whether the block is in use, routable, or reachable.
  • IPv4 only. IPv6 subnetting works on nibble boundaries and a 128-bit address space, and squeezing it into this form would produce wrong answers.
  • Reports the usable range as the standard defines it. Some equipment can be configured to use the network or broadcast address anyway, and some networks reserve extra addresses for gateways and DHCP by local convention.
  • Non-contiguous masks such as 255.0.255.0 are rejected rather than converted. They are legal in the original specification, no modern stack accepts one, and the nearest prefix would describe a different subnet.

Take this with you

IP Subnet Calculator on RunTheTests — free browser-based netmath tools, no sign-up.