CIDR Calculator
Calculate subnet details, host ranges, and masks from CIDR notation. Runs entirely in your browser.
CIDR Notation
Quick Presets
Subnet Details
Network Address
Broadcast Address
Subnet Mask
Wildcard Mask
First Usable Host
Last Usable Host
Total Hosts
Usable Hosts
CIDR Prefix
IP Class
Network Address (Binary)
IP Range
Specifications
- Accepts
- No file needed
- Gives you
- On-screen result
- Where it runs
- Your browser — the file is never uploaded
- Sign-up
- None
- Cost
- Free, with no usage limits
Understanding CIDR Notation
CIDR (Classless Inter-Domain Routing) notation expresses an IP address and its associated network prefix as IP/prefix, e.g. 192.168.1.0/24.
- The prefix length (after the slash) is the number of bits in the network part.
/24means 24 network bits and 8 host bits. - The subnet mask is derived from the prefix:
/24 → 255.255.255.0. - The network address is the first address in the range (all host bits = 0). The broadcast address is the last (all host bits = 1).
- Usable hosts = Total hosts − 2 (network and broadcast addresses are reserved), except for /31 (point-to-point links) and /32 (single host).
- /30 gives 2 usable hosts — the smallest subnet for a point-to-point link with traditional addressing.