IP Subnet Calculator
Calculate IPv4 network address, broadcast address, CIDR notation, wildcard mask and usable host range.
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Result
Enter IP and subnet mask, then click Calculate.
About IP Subnet Calculator
This IPv4 subnet calculator computes network address, broadcast address, CIDR notation, wildcard mask, and usable host range from an IP address and subnet mask (or CIDR prefix).
It is useful for network planning, subnet design, firewall rule configuration, VLAN setup, and understanding IP addressing for both IPv4 networks.
Subnet Calculation Formulas
IP to 32-bit number: n = (octet1 << 24) + (octet2 << 16) + (octet3 << 8) + octet4 Example: 192.168.1.100 → 3232235876 CIDR to subnet mask: mask = (0xFFFFFFFF << (32 - cidr)) & 0xFFFFFFFF /24: 11111111.11111111.11111111.00000000 = 255.255.255.0 Network address (bitwise AND): network = ip & mask 192.168.1.100 & 255.255.255.0 = 192.168.1.0 Broadcast address: wildcard = ~mask (bitwise NOT) broadcast = network | wildcard 192.168.1.0 | 0.0.0.255 = 192.168.1.255 Usable hosts: hosts = 2^(32 - cidr) - 2 /24: 2^8 - 2 = 254 hosts First host: network + 1 Last host: broadcast - 1
Common Subnet Masks Reference
| CIDR | Subnet Mask | Wildcard | Total IPs | Usable Hosts |
|---|---|---|---|---|
/32 | 255.255.255.255 | 0.0.0.0 | 1 | 1 (single host) |
/30 | 255.255.255.252 | 0.0.0.3 | 4 | 2 (point-to-point) |
/29 | 255.255.255.248 | 0.0.0.7 | 8 | 6 |
/28 | 255.255.255.240 | 0.0.0.15 | 16 | 14 |
/27 | 255.255.255.224 | 0.0.0.31 | 32 | 30 |
/26 | 255.255.255.192 | 0.0.0.63 | 64 | 62 |
/25 | 255.255.255.128 | 0.0.0.127 | 128 | 126 |
/24 | 255.255.255.0 | 0.0.0.255 | 256 | 254 |
/23 | 255.255.254.0 | 0.0.1.255 | 512 | 510 |
/22 | 255.255.252.0 | 0.0.3.255 | 1,024 | 1,022 |
/21 | 255.255.248.0 | 0.0.7.255 | 2,048 | 2,046 |
/20 | 255.255.240.0 | 0.0.15.255 | 4,096 | 4,094 |
/19 | 255.255.224.0 | 0.0.31.255 | 8,192 | 8,190 |
/18 | 255.255.192.0 | 0.0.63.255 | 16,384 | 16,382 |
/17 | 255.255.128.0 | 0.0.127.255 | 32,768 | 32,766 |
/16 | 255.255.0.0 | 0.0.255.255 | 65,536 | 65,534 |
/12 | 255.240.0.0 | 0.15.255.255 | 1,048,576 | 1,048,574 |
/8 | 255.0.0.0 | 0.255.255.255 | 16,777,216 | 16,777,214 |
Private IP Address Ranges
| Class | Range | CIDR | Use Case |
|---|---|---|---|
| Class A | 10.0.0.0 – 10.255.255.255 | 10.0.0.0/8 | Large networks |
| Class B | 172.16.0.0 – 172.31.255.255 | 172.16.0.0/12 | Medium networks |
| Class C | 192.168.0.0 – 192.168.255.255 | 192.168.0.0/16 | Small/home networks |
| Loopback | 127.0.0.0 – 127.255.255.255 | 127.0.0.0/8 | Localhost testing |
Calculation Example
Input:
IP: 192.168.1.100
Mask: 255.255.255.0 (or /24)
Step 1: Convert to binary
IP: 11000000.10101000.00000001.01100100
Mask: 11111111.11111111.11111111.00000000
Step 2: AND for network
Network: 11000000.10101000.00000001.00000000
= 192.168.1.0
Step 3: Invert mask for wildcard
Wildcard: 00000000.00000000.00000000.11111111
= 0.0.0.255
Step 4: OR for broadcast
Broadcast: 11000000.10101000.00000001.11111111
= 192.168.1.255
Results:
Network: 192.168.1.0/24
Broadcast: 192.168.1.255
First Host: 192.168.1.1
Last Host: 192.168.1.254
Usable: 254 hosts
Frequently Asked Questions
- What is a subnet mask?
- A subnet mask divides an IP address into network and host portions. Written as 255.255.255.0 or /24 (CIDR). The 1 bits represent the network, 0 bits represent hosts. Common masks: /24 (255.255.255.0) = 254 hosts, /16 (255.255.0.0) = 65,534 hosts, /32 = single host.
- What is CIDR notation?
- CIDR (Classless Inter-Domain Routing) notation uses a slash followed by the number of network bits: /24 means 24 bits for network, 8 for hosts. Replaced classful addressing (Class A/B/C). Example: 192.168.1.0/24 = network 192.168.1.0 with mask 255.255.255.0.
- What is the network address?
- The network address is the first address in a subnet (all host bits = 0). It identifies the subnet itself and cannot be assigned to hosts. Calculated by ANDing the IP address with the subnet mask. Example: 192.168.1.100/24 → network 192.168.1.0.
- What is the broadcast address?
- The broadcast address is the last address in a subnet (all host bits = 1). Packets sent to this address reach all hosts in the subnet. Calculated by ORing the network address with the wildcard mask. Example: 192.168.1.0/24 → broadcast 192.168.1.255.
- What is a wildcard mask?
- A wildcard mask is the inverse of a subnet mask (bits flipped). Used in ACLs and routing. Example: subnet 255.255.255.0 → wildcard 0.0.0.255. Calculated by subtracting each octet from 255. Wildcard = ~subnet_mask (bitwise NOT).
- How many usable hosts per subnet?
- Formula: 2^(host_bits) - 2. Subtract 2 for network and broadcast addresses. /24 = 8 host bits = 254 hosts, /25 = 7 bits = 126 hosts, /26 = 6 bits = 62 hosts, /30 = 2 bits = 2 hosts (point-to-point links).