IPv4 & IPv6 Subnet Calculator
Enter an IP address with its prefix (CIDR) to see the network, broadcast, host range, netmask and wildcard. You can also split the block into smaller subnets.
| # | Network | Host range | Broadcast |
|---|
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How to read the subnet calculator results
An IPv4 address is 32 bits long. The prefix (the number after the slash) sets how many bits belong to the network part; the rest form the host part. Take 192.168.10.25/26: 26 bits for the network and 6 bits for hosts, so the subnet holds 26 = 64 addresses, 62 of which can be assigned to devices.
- Network address: the first address, representing the subnet itself in the routing table.
- Broadcast: the last address, used to send packets to every host in the subnet.
- Host range: the addresses you can assign to servers, routers and other devices.
- Wildcard mask: the inverse of the subnet mask, used in ACLs and OSPF.
IPv4 CIDR table (/8 to /32)
| Prefix | Subnet mask | Total addresses | Usable hosts |
|---|---|---|---|
| /8 | 255.0.0.0 | 16,777,216 | 16,777,214 |
| /9 | 255.128.0.0 | 8,388,608 | 8,388,606 |
| /10 | 255.192.0.0 | 4,194,304 | 4,194,302 |
| /11 | 255.224.0.0 | 2,097,152 | 2,097,150 |
| /12 | 255.240.0.0 | 1,048,576 | 1,048,574 |
| /13 | 255.248.0.0 | 524,288 | 524,286 |
| /14 | 255.252.0.0 | 262,144 | 262,142 |
| /15 | 255.254.0.0 | 131,072 | 131,070 |
| /16 | 255.255.0.0 | 65,536 | 65,534 |
| /17 | 255.255.128.0 | 32,768 | 32,766 |
| /18 | 255.255.192.0 | 16,384 | 16,382 |
| /19 | 255.255.224.0 | 8,192 | 8,190 |
| /20 | 255.255.240.0 | 4,096 | 4,094 |
| /21 | 255.255.248.0 | 2,048 | 2,046 |
| /22 | 255.255.252.0 | 1,024 | 1,022 |
| /23 | 255.255.254.0 | 512 | 510 |
| /24 | 255.255.255.0 | 256 | 254 |
| /25 | 255.255.255.128 | 128 | 126 |
| /26 | 255.255.255.192 | 64 | 62 |
| /27 | 255.255.255.224 | 32 | 30 |
| /28 | 255.255.255.240 | 16 | 14 |
| /29 | 255.255.255.248 | 8 | 6 |
| /30 | 255.255.255.252 | 4 | 2 |
| /31 | 255.255.255.254 | 2 | 2 |
| /32 | 255.255.255.255 | 1 | 1 |
Special IPv4 ranges to know
10.0.0.0/8,172.16.0.0/12,192.168.0.0/16: private addresses (RFC 1918), not routed on the internet.100.64.0.0/10: shared address space for CGNAT in ISP networks (RFC 6598).169.254.0.0/16: link-local, seen when a device fails to get a DHCP lease.127.0.0.0/8: loopback.
IPv6 subnetting
IPv6 uses 128 bits and has no broadcast. Common practice: each VLAN or LAN segment uses a /64, while each site receives a /48 or /56. This calculator shows how many /64s fit inside the prefix you enter.
Frequently asked questions
What are a subnet and CIDR?
A subnet is a smaller block carved out of a larger IP network. CIDR (Classless Inter-Domain Routing) writes the size of that block as a slash followed by the prefix length. For example, 192.168.1.0/24 means the first 24 bits are the network part and the remaining 8 bits are for hosts.
Why is the number of usable hosts always two less?
In IPv4, the first address of a subnet is the network address and the last is the broadcast address, so neither is assigned to a device. The exceptions are /31 (two addresses, used for point-to-point links per RFC 3021) and /32 (a single address).
What is the difference between a subnet mask and a wildcard mask?
A subnet mask marks the network bits with 1s, for example 255.255.255.0. A wildcard mask is its inverse (0.0.0.255) and is widely used in router ACLs and OSPF configuration.
What subnet sizes are common in IPv6?
A single IPv6 LAN segment almost always uses a /64. A customer or site usually receives a /48 or /56, which contains 65,536 or 256 /64s respectively. IPv6 has no broadcast address.
Is the IP address I enter stored?
No. All calculations run in your browser and no data is sent to Cloudku servers.
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