CIDR Calculator
Calculate IPv4 and IPv6 CIDR address ranges, subnet information and host counts.
CIDR input
Format: IP address / prefix length (e.g. 192.168.1.0/24)
About CIDR
CIDR notation — Classless Inter-Domain Routing.
Prefix length — Number of bits used for the network portion.
• /8 = 255.0.0.0 (Class A default)
• /16 = 255.255.0.0 (Class B default)
• /24 = 255.255.255.0 (Class C default)
• /30 = 255.255.255.252 (point-to-point)
Special addresses：
• Network address — cannot be assigned to a host.
• Broadcast address — used for broadcasts.
• Usable IPs = total − 2 (network + broadcast).
Related tools
What does CIDR Calculator do?
Calculate IPv4 and IPv6 CIDR address ranges, subnet information and host counts. Compare prefix lengths when planning networks or reviewing address allocation rules.
Interpreting results and common questions
Do IPv4 and IPv6 use the same host-count rules?
A CIDR prefix determines block size, but IPv4 network and broadcast rules do not directly apply to IPv6. Assignable ranges also depend on link type and network configuration.
References and result limitations
Local results depend on the input and selected options. Retain the input example, format and processing rules when citing a result, and verify the output. Keep keys and other sensitive material out of public examples.
These references explain protocol or format rules; they do not endorse results produced by this site.