How do I calculate a subnet from an IP address?

Enter the IP above with a CIDR prefix (e.g. 192.168.1.0/24) or a subnet mask. The tool computes the network address, broadcast address, usable host range, wildcard mask, and binary breakdown instantly — free, no signup, in your browser.

What is the difference between a subnet mask and a wildcard mask?

The subnet mask marks network bits with 1s (e.g. 255.255.255.0); the wildcard mask is its bitwise inverse (0.0.0.255) and is used in router ACLs and OSPF network statements. This tool shows both for every calculation.

How many usable hosts are in a /24 subnet?

254. A /24 has 256 total addresses minus the network address and the broadcast address. Try 192.168.1.0 with CIDR 24 above to see the full breakdown including first usable (192.168.1.1) and last usable (192.168.1.254).

What is CIDR notation?

CIDR notation writes the network as IP/prefix-length, e.g. 192.168.1.0/24, where 24 means the first 24 bits are the network portion. Larger prefix = smaller subnet. This tool converts both directions: CIDR to dotted mask and dotted mask to CIDR.

Why does the tool reject my subnet mask?

A valid subnet mask must be contiguous — all 1-bits followed by all 0-bits (e.g. 255.255.240.0 is fine, 255.0.255.0 is not). Non-contiguous masks are invalid in IP networking, so the tool refuses them rather than guessing.

IPv4 Subnet Calculator — Network & Broadcast Online

What is Subnet calculator?

IPv4 Subnet Calculator — Free IPv4 subnet calculator — enter an IP with CIDR or netmask to get network, broadcast, usable range, wildcard mask and binary notation. Pure math, runs in your browser.

Zero dependencies — all math is unsigned 32-bit integer arithmetic written for this tool: dotted-quad to uint32 conversion, netmask = 0xFFFFFFFF << (32 − prefix), network = IP & mask, broadcast = network | ~mask, wildcard = ~mask. Non-contiguous masks (e.g. 255.0.255.0) are rejected because they are not valid subnet masks. /31 and /32 are handled per RFC 3021 semantics and reported honestly (a /32 is a single host; a /31 has no traditionally-usable addresses). Private-range detection follows RFC 1918 (10/8, 172.16/12, 192.168/16). Everything runs client-side; nothing is uploaded.

Why use this subnet calculator?

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Built for subnet calculator

Free IPv4 subnet calculator — enter an IP with CIDR or netmask to get network, broadcast, usable range, wildcard mask and binary notation. Pure math, runs in your browser.

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Transparent & honest

IPv4 only — IPv6 subnets use a different (128-bit) scheme and are not covered.

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Private by design

Everything runs in your browser. Your inputs never leave your device.

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Works everywhere

Fully responsive — perfect on desktop, tablet, and mobile. No app needed.

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Regularly updated

Regularly maintained and reviewed to ensure accuracy.

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Free forever

No accounts, no limits, no watermarks. Use IPv4 Subnet Calculator as much as you need.

How to use IPv4 Subnet Calculator

1Type an IPv4 address into the "IP address" field, e.g. 192.168.1.0.
2Enter either a CIDR prefix (0–32, e.g. 24) or a subnet mask (e.g. 255.255.255.0) — one is required.
3Run the tool to compute the subnet from pure 32-bit integer math.
4Read the network address, broadcast address, and first/last usable host range.
5Use the wildcard mask for ACLs and the binary notation to see exactly which bits are network vs host.

What can you do with IPv4 Subnet Calculator?

Ipv4 subnet calculator online — Free IPv4 subnet calculator — enter an IP with CIDR or netmask to get network, broadcast, usable range, wildcard mask and binary notation.
Cidr calculator — Free IPv4 subnet calculator — enter an IP with CIDR or netmask to get network, broadcast, usable range, wildcard mask and binary notation.
Network broadcast calculator — Free IPv4 subnet calculator — enter an IP with CIDR or netmask to get network, broadcast, usable range, wildcard mask and binary notation.
Subnet mask calculator — Free IPv4 subnet calculator — enter an IP with CIDR or netmask to get network, broadcast, usable range, wildcard mask and binary notation.

Good to know

IPv4 only — IPv6 subnets use a different (128-bit) scheme and are not covered.
Usable-host counts exclude network and broadcast addresses, the standard convention for host subnets.
/31 subnets report 0 traditionally-usable hosts; both addresses are usable on RFC 3021 point-to-point links.

How it works

Zero dependencies — all math is unsigned 32-bit integer arithmetic written for this tool: dotted-quad to uint32 conversion, netmask = 0xFFFFFFFF << (32 − prefix), network = IP & mask, broadcast = network | ~mask, wildcard = ~mask. Non-contiguous masks (e.g. 255.0.255.0) are rejected because they are not valid subnet masks. /31 and /32 are handled per RFC 3021 semantics and reported honestly (a /32 is a single host; a /31 has no traditionally-usable addresses). Private-range detection follows RFC 1918 (10/8, 172.16/12, 192.168/16). Everything runs client-side; nothing is uploaded.

Examples

Classic /24 home network

Status: ok — network 192.168.1.0, broadcast 192.168.1.255, usable 192.168.1.1–192.168.1.254 (254 hosts), mask 255.255.255.0.

Netmask input instead of CIDR

Status: ok — treated as /16: network 10.0.0.0, broadcast 10.0.255.255, 65,534 usable hosts.

Invalid mask rejected

Status: error — 255.0.255.0 is not a contiguous mask; mask bits must be leading 1s followed by 0s.

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