IPv4 subnet calculator
Type an IP address with a prefix (10.0.0.0/16) or a mask (192.168.1.10 255.255.255.0). The results update as you type, and you can split the range into smaller subnets.
192.168.10.0/24
| Network address | 192.168.10.0 |
|---|---|
| Subnet mask | 255.255.255.0 (/24) |
| Wildcard mask | 0.0.0.255 |
| Broadcast address | 192.168.10.255 |
| Usable host range | 192.168.10.1 – 192.168.10.254 |
| Usable hosts | 254 |
| Total addresses | 256 |
| Azure usable hosts | 251 |
| Address type | Private (RFC 1918) |
How to use it
- Enter any address inside the range with its prefix, for example
172.16.5.20/22. The tool finds the network the address belongs to. - Read the usable host range and host count. For Azure virtual networks, use the Azure row: Azure reserves 5 addresses in every subnet.
- To plan a VNet or VLAN layout, choose a smaller prefix under Split into smaller subnets.
Quick reference
/24: 256 addresses, 254 usable (251 in Azure)./26: 64 addresses, 62 usable (59 in Azure)./27: 32 addresses, the minimum Microsoft recommends for an Azure VPN gateway subnet./29: 8 addresses, the smallest Azure subnet./31: 2 addresses for point-to-point links (RFC 3021), both usable.
Related guides
Questions people ask
Why does Azure give me 5 fewer addresses?
Azure reserves the network address, the first three host addresses (default gateway and two for Azure DNS) and the broadcast address in every subnet. A /24 subnet in Azure has 251 usable addresses.
What is a wildcard mask?
The inverse of the subnet mask, used in Cisco ACLs and OSPF statements. For 255.255.255.0 it is 0.0.0.255.
Which ranges are private?
10.0.0.0/8, 172.16.0.0/12 and 192.168.0.0/16 (RFC 1918). 100.64.0.0/10 is reserved for carrier-grade NAT, and 169.254.0.0/16 is link-local (APIPA).
Does it support IPv6?
Not yet. IPv6 subnets are almost always /64 for LANs, so the planning question is usually how many /64s fit in your allocation: a /56 holds 256, a /48 holds 65,536.