Advanced CIDR Calculator
Convert between CIDR notation, subnet masks, wildcard masks, and calculate network ranges
Tip: Enter any IP address with CIDR notation (e.g., 192.168.1.0/24) to calculate all network properties.
Network Information
Network Properties
Network Address:-
Broadcast Address:-
First Usable IP:-
Last Usable IP:-
Addressing Details
Total Hosts:-
Usable Hosts:-
Subnet Bits:-
Host Bits:-
Binary Representation
| IP Address | Subnet Mask | Network Address |
|---|---|---|
| - | - | - |
IP Range
-
Understanding CIDR Notation: A Network Professional's Guide
CIDR Basics
- CIDR (Classless Inter-Domain Routing) replaced classful networking
- The notation indicates network bits after the slash (e.g., /24)
- Allows for flexible subnet sizes beyond Class A/B/C limitations
Common CIDR Blocks
- /32: Single host (255.255.255.255)
- /24: Classic Class C (255.255.255.0)
- /16: Classic Class B (255.255.0.0)
- /8: Classic Class A (255.0.0.0)
"Proper subnetting with CIDR can reduce IP address waste by up to 70% compared to classful addressing."
CIDR Cheat Sheet: Quick Reference
| CIDR | Subnet Mask | Wildcard | Hosts |
|---|---|---|---|
| /32 | 255.255.255.255 | 0.0.0.0 | 1 |
| /30 | 255.255.255.252 | 0.0.0.3 | 2 |
| /24 | 255.255.255.0 | 0.0.0.255 | 254 |
| /16 | 255.255.0.0 | 0.0.255.255 | 65,534 |
| /8 | 255.0.0.0 | 0.255.255.255 | 16,777,214 |
Note: The number of usable hosts is always 2 less than the total (network and broadcast addresses cannot be assigned to hosts).
CIDR Calculator FAQs
What is CIDR notation used for?
CIDR (Classless Inter-Domain Routing) notation is used to specify the network portion of an IP address. It allows for more flexible allocation of IP addresses than the old classful networking system, enabling efficient use of the limited IPv4 address space.
How do I calculate the number of hosts from a CIDR?
The formula is: 2^(32 - CIDR) - 2. For example, a /24 network has 2^(32-24) - 2 = 256 - 2 = 254 usable hosts. The subtraction accounts for the network and broadcast addresses which can't be assigned to hosts.
What's the difference between subnet mask and wildcard mask?
A subnet mask identifies the network portion of an IP address (1s for network, 0s for hosts). A wildcard mask is the inverse - it identifies the host portion (0s for network, 1s for hosts). For example, subnet 255.255.255.0 = wildcard 0.0.0.255.
Can I use this calculator for IPv6 addresses?
This calculator is designed for IPv4 addresses only. IPv6 uses a different addressing scheme and much larger address space, though it also uses CIDR notation (with prefix lengths up to /128).
Why does my network have two fewer usable addresses than the total?
Every subnet has a network address (identifies the subnet itself) and a broadcast address (for sending to all hosts on the subnet). These two addresses cannot be assigned to individual hosts, hence the "-2" in host calculations.