Subnet Calculator
Calculate network, broadcast, and host ranges from CIDR
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About this tool
Enter an IPv4 address and CIDR to calculate the network address, broadcast address, subnet mask, wildcard mask, and the range and count of usable hosts. It also flags whether the range is a private block (RFC1918) or a special-purpose block like loopback, link-local, multicast, or CGNAT, and lets you view a list split into smaller subnets.
How to use
- Enter it in `192.168.0.0/24` format, or write the mask out (`192.168.0.0 255.255.255.0`).
- Check the network address, broadcast address, subnet mask, and wildcard mask.
- Check the usable host range and count, whether it is private or public, and any special-purpose block.
- To split it further, pick a target prefix and view the list of resulting subnets.
- Tap any value to copy it to the clipboard.
Frequently asked questions
- Why are there 2 fewer usable addresses than the total?
- The network address (the first address in the range) and the broadcast address (the last one) cannot be assigned to a device, so only total minus 2 addresses are actually usable.
- Why are /31 and /32 different?
- /31 is dedicated to point-to-point links and uses both addresses as hosts (RFC 3021). /32 is a host route with exactly one address.
- What is the wildcard mask used for?
- It is used in place of a subnet mask in things like router ACLs (access control lists). Its bits are the exact inverse of the subnet mask's (1s and 0s swapped).
- Does this support IPv6?
- Only IPv4 is supported right now.
- How are private and special-purpose blocks distinguished?
- 10.0.0.0/8, 172.16.0.0/12, and 192.168.0.0/16 are RFC1918 private blocks. Special-purpose blocks such as 127.0.0.0/8 (loopback), 169.254.0.0/16 (link-local), 224.0.0.0/4 (multicast), and 100.64.0.0/10 (CGNAT) are also flagged.
This calculator only shows IPv4 CIDR calculation results. It is separate from your actual network hardware's routing or firewall configuration, and IPv6 is not supported.