IP Subnet Calculator Online
Enter any IPv4 address and CIDR prefix to instantly calculate network address, broadcast address, first and last host, usable hosts, subnet mask, and wildcard mask. Includes subnet division, binary view, VLSM, and supernetting tools.
How to Use the Subnet Calculator
Enter an IPv4 address in dotted decimal notation (e.g., 192.168.1.0) and a CIDR prefix (e.g., /24). The calculator immediately shows all subnet details: network address, broadcast address, first/last usable hosts, subnet mask, and wildcard mask.
The Extended Calculator lets you split a network into equal subnets and view binary representations. The Professional Calculator handles VLSM (variable-length subnet masking), supernetting/CIDR aggregation, and basic IPv6 information.
Divide Network into Equal Subnets
| # | Network | First Host | Last Host | Broadcast |
|---|---|---|---|---|
| 1 | 192.168.1.0/26 | 192.168.1.1 | 192.168.1.62 | 192.168.1.63 |
| 2 | 192.168.1.64/26 | 192.168.1.65 | 192.168.1.126 | 192.168.1.127 |
| 3 | 192.168.1.128/26 | 192.168.1.129 | 192.168.1.190 | 192.168.1.191 |
| 4 | 192.168.1.192/26 | 192.168.1.193 | 192.168.1.254 | 192.168.1.255 |
Understanding IP Subnet Masks
A subnet mask is a 32-bit number that separates the network portion of an IP address from the host portion. Written in dotted decimal (e.g., 255.255.255.0) or CIDR notation (/24), it determines which addresses belong to the same subnet.
| CIDR | Subnet Mask | Hosts | Typical Use |
|---|---|---|---|
| /8 | 255.0.0.0 | 16,777,214 | Class A — very large networks |
| /16 | 255.255.0.0 | 65,534 | Class B — large enterprises |
| /24 | 255.255.255.0 | 254 | Standard office LAN |
| /26 | 255.255.255.192 | 62 | Department segment |
| /28 | 255.255.255.240 | 14 | Small team |
| /30 | 255.255.255.252 | 2 | Point-to-point WAN link |
Private IP Address Ranges (RFC 1918)
| Range | CIDR | Addresses | Class |
|---|---|---|---|
| 10.0.0.0 – 10.255.255.255 | 10.0.0.0/8 | 16,777,216 | A |
| 172.16.0.0 – 172.31.255.255 | 172.16.0.0/12 | 1,048,576 | B |
| 192.168.0.0 – 192.168.255.255 | 192.168.0.0/16 | 65,536 | C |
These addresses are not routable on the public internet. All home routers and corporate LANs use these ranges. The 192.168.x.x range is the most commonly seen in home networks.
Variable Length Subnet Masking (VLSM)
Allocates subnets efficiently from largest to smallest requirement.
| Department / Network | Hosts Needed | |
|---|---|---|
VLSM Allocation
| Name | Subnet | CIDR | Usable Hosts | Waste |
|---|---|---|---|---|
| Sales Dept | 192.168.1.0/26 | /26 | 62 | 12 |
| Engineering | 192.168.1.64/27 | /27 | 30 | 0 |
| Management | 192.168.1.96/28 | /28 | 14 | 4 |
| DMZ | 192.168.1.112/29 | /29 | 6 | 1 |