IPv4 CIDR Calculator — Subnet, Free | How to use and interpret results
Calculate an IPv4 network, mask and address range from an address and prefix length. This explains bit boundaries without inspecting a router or live host allocation.
- Runs in your browser
- Nothing is uploaded
- No signup; device limits apply
Numbers stay on your device. Nothing is sent to a server.
How to use this tool
Enter four dotted octets and a prefix from 0 through 32. Do not substitute an IPv6 address or netmask string, and check the addressing policy of the intended network.
Results and examples
192.168.1.10/24 gives network 192.168.1.0 and mask 255.255.255.0. A conventional /24 has hosts .1 through .254; /31 and /32 use separate host-count conventions.
Worked example
192.168.1.10/24 gives network 192.168.1.0 and mask 255.255.255.0. A conventional /24 has hosts .1 through .254; /31 and /32 use separate host-count conventions.
Limitations
- Routing, DHCP reservations, firewall policy and occupied addresses are not queried.
- Special-purpose addresses and link support for /31 require environment-specific review.
Fields
| Field | Guidance and constraints |
|---|---|
| IPv4 address | Check the unit and format displayed beside this field. |
| Prefix length | Accepted range: 0–32 · Input step: 1 |
Data handling
Processing stays in the current browser tab; the site does not upload tool input for the calculation itself.
Sources
Frequently asked questions
What network contains 192.168.1.10/24?
192.168.1.10/24 gives network 192.168.1.0 and mask 255.255.255.0. A conventional /24 has hosts .1 through .254; /31 and /32 use separate host-count conventions.
Can I immediately assign every address in the range?
Routing, DHCP reservations, firewall policy and occupied addresses are not queried. Special-purpose addresses and link support for /31 require environment-specific review.
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