CIDR & Subnet Calculator
Runs in your browserCalculate network, broadcast, mask, wildcard, usable range and host count for any IPv4 or IPv6 CIDR block. Everything runs locally in your browser.
How to read the results
The network address identifies the subnet itself; the broadcast address (IPv4) is the all-ones host address. The usable range is what you can assign to devices. Total addresses counts every address in the block, while usable hosts excludes the network and broadcast addresses for prefixes shorter than /31.
How to use it
- Choose the IPv4 or IPv6 tab.
- Enter an address in CIDR form (e.g.
10.0.0.0/8) or type the address and prefix separately. - Select Calculate. Copy any value with its copy button.
Examples
192.168.1.10/24→ network192.168.1.0, broadcast192.168.1.255, 254 usable hosts.10.0.0.0/30→ 2 usable hosts (a typical point-to-point /30).2001:db8::/48→ 2⁸⁰ addresses.
Common issues
- Leading zeros like
192.168.01.1are rejected as ambiguous — remove them. - Prefix out of range — IPv4 prefixes are 0–32, IPv6 are 0–128.
Special cases
/31 and /32 are treated according to RFC 3021 and host-route conventions, not the general subnet rules. Large blocks are computed with BigInt so address counts never overflow.
All calculations run locally in your browser; no data leaves your device. Learn about our data sources →
Frequently asked questions
What is the difference between a /24 and a subnet mask of 255.255.255.0?
They describe the same thing. The CIDR prefix
/24 means the first 24 bits are the network portion, which equals the mask 255.255.255.0.Why does a /31 show two usable hosts?
Per RFC 3021, /31 networks are used on point-to-point links where there is no need for network or broadcast addresses, so both addresses are usable.
How many hosts can a /32 hold?
A /32 describes a single host (a host route). The network and host address are the same.
Does this tool send my input to a server?
No. All subnet calculations run entirely in your browser using JavaScript BigInt math. Nothing is transmitted.