IPv4 CIDR Calculator
Calculate IPv4 address ranges using CIDR notation. Determine network addresses, broadcast addresses, and host ranges for your subnet planning.
Private IPv4 Addresses (RFC 1918)
Private IPv4 addresses are reserved for use within private networks and are not routable on the public internet. These addresses are commonly used in home and corporate networks.
| RFC 1918 Name | Address Range | Number of Addresses | Largest CIDR | Host ID Size | Mask Bits | Description |
|---|---|---|---|---|---|---|
| 24-bit Block | 10.0.0.0 - 10.255.255.255 |
16,777,216 | 10.0.0.0/8 |
24 bits | 8 bits | Single Class A network |
| 20-bit Block | 172.16.0.0 - 172.31.255.255 |
1,048,576 | 172.16.0.0/12 |
20 bits | 12 bits | 16 Contiguous Class B Networks |
| 16-bit Block | 192.168.0.0 - 192.168.255.255 |
65,536 | 192.168.0.0/16 |
16 bits | 16 bits | 256 Contiguous Class C Networks |
Common Private IPv4 CIDR Ranges
An IPv4 CIDR Range is a way to specify a range of IP addresses using CIDR notation. CIDR notation uses a compact representation of an IP address and its associated network mask to specify the number of bits in the subnet mask.
Class A (10.0.0.0/8)
Class B (172.16.0.0/12)
Class C (192.168.0.0/16)
CIDR Reference Table
This table shows acceptable CIDR values for IPv4 addresses, their corresponding subnet masks, and the number of available hosts:
| CIDR | Subnet Mask | Hosts |
|---|---|---|
/0 |
255.0.0.0 |
4,294,967,296 |
/1 |
255.0.0.0 |
2,147,483,648 |
/2 |
255.0.0.0 |
1,073,741,824 |
/3 |
255.0.0.0 |
536,870,912 |
/4 |
255.0.0.0 |
268,435,456 |
/5 |
255.0.0.0 |
134,217,728 |
/6 |
255.0.0.0 |
67,108,864 |
/7 |
255.0.0.0 |
33,554,432 |
/8 |
255.255.0.0 |
16,777,216 |
/9 |
255.255.0.0 |
8,388,608 |
/10 |
255.255.0.0 |
4,194,304 |
/11 |
255.255.0.0 |
2,097,152 |
/12 |
255.255.0.0 |
1,048,576 |
/13 |
255.255.0.0 |
524,288 |
/14 |
255.255.0.0 |
262,144 |
/15 |
255.255.0.0 |
131,072 |
/16 |
255.255.255.0 |
65,536 |
/17 |
255.255.255.0 |
32,768 |
/18 |
255.255.255.0 |
16,384 |
/19 |
255.255.255.0 |
8,192 |
/20 |
255.255.255.0 |
4,096 |
/21 |
255.255.255.0 |
2,048 |
/22 |
255.255.255.0 |
1,024 |
/23 |
255.255.255.0 |
512 |
/24 |
255.255.255.255 |
256 |
/25 |
255.255.255.255 |
128 |
/26 |
255.255.255.255 |
64 |
/27 |
255.255.255.255 |
32 |
/28 |
255.255.255.255 |
16 |
/29 |
255.255.255.255 |
8 |
/30 |
255.255.255.255 |
4 |
/31 |
255.255.255.255 |
2 |
/32 |
255.255.255.255 |
1 |
Note: The number of hosts is calculated as 2^(32 - CIDR). A /32 has 1 address (host), and /0 has 4,294,967,296 addresses.
IPv4 Fundamentals
IPv4 is a fundamental part of the internet and is used by billions of devices every day. Understanding IPv4 is essential for networking, system administration, and IT professionals.
- IPv4 is a 32-bit address space, supporting 2^32 (~4.3 billion) addresses.
- IPv4 addresses are typically written as four decimal numbers (0-255) separated by periods.
- IPv4 addresses are divided into classes: A, B, C, D, and E.
- Public addresses are routable on the internet; private addresses are for local networks only.
- IPv4 addresses are usually assigned via DHCP (Dynamic Host Configuration Protocol).
- Addresses can be assigned statically for servers and fixed infrastructure.
- IPv4 addresses can be subnetted using subnet masks for network segmentation.
- CIDR notation enables flexible subnetting without class-based boundaries.
- IPv6 was developed due to IPv4 address exhaustion (128-bit vs 32-bit).
- NAT (Network Address Translation) allows multiple devices to share one public IP.