How do I use this IP subnet calculator?

Paste an IPv4 CIDR such as 192.168.1.10/24 (or a bare IP with the prefix override). The page shows network, broadcast, host range, masks, and host counts immediately. Nothing is uploaded.

What is CIDR notation?

CIDR appends a slash and prefix length to an IP (e.g. /24). The prefix is how many leading bits belong to the network; the rest are host bits. /24 means a 255.255.255.0 mask and 256 addresses.

How are usable hosts calculated?

For prefixes shorter than /31, usable hosts = total addresses minus network and broadcast. /31 follows RFC 3021 (both addresses usable). /32 is a single host route with 1 usable address.

What is the difference between subnet mask and wildcard mask?

The subnet mask has 1-bits for the network portion (e.g. 255.255.255.0). The wildcard mask is the inverse (0.0.0.255) and appears in some ACL and OSPF configs.

Does this support IPv6?

Not yet. This tool focuses on IPv4 CIDR math - network, broadcast, host range, and masks for 0-32 prefixes.

Is my IP address uploaded?

No. All calculation runs locally in this tab. Addresses never leave your browser.

Why does /31 look different from other prefixes?

RFC 3021 allows /31 on point-to-point links so both addresses can be used as hosts. There is no classic unused broadcast address in that mode.

What does IP class mean here?

The classical A-E letter from the first octet (historical). Modern networks use CIDR, but class still appears in older docs and exams.

Calculator Tools

IP Subnet Calculator

Paste an IPv4 address with a CIDR prefix (for example `192.168.1.10/24`) and get structured network math instantly: network address, broadcast, first and last usable hosts,…

All IPv4 CIDR math runs in your browser. Nothing is uploaded.

IPv4 address or CIDR

Paste an address with a prefix (e.g. 10.0.0.5/24) or enable the prefix override below.

Quick prefixes

Use separate prefix length

Network address

192.168.1.0

Broadcast address

192.168.1.255

First usable host

192.168.1.1

Last usable host

192.168.1.254

Subnet mask

255.255.255.0

Wildcard mask

0.0.0.255

Network CIDR

192.168.1.0/24

Total addresses

256

Usable hosts

254

IP class

Class C

Host range: 192.168.1.1 - 192.168.1.254

About IP Subnet Calculator

Paste an IPv4 address with a CIDR prefix (for example `192.168.1.10/24`) and get structured network math instantly: network address, broadcast, first and last usable hosts, subnet mask, wildcard mask, total addresses, and usable host count. Everything runs in your browser - nothing is uploaded. Use it when sizing LAN segments, checking a firewall rule, or converting slash notation to a dotted mask. Pair it with other developer session tools like the UUID Generator when you are wiring infrastructure configs.

How to Use IP Subnet Calculator

Enter an IPv4 address with a CIDR prefix, such as 192.168.1.10/24.
Or enable the separate prefix length and type a bare IP plus 0-32.
Read network, broadcast, host range, masks, and host counts as you type.
Use Quick prefixes (/8, /16, /24, /30, /32) to load common examples.
Copy the summary when you need the values in a ticket or config.

IP Subnet Calculator Examples

Classic /24 LAN

192.168.1.10/24 yields network 192.168.1.0, broadcast 192.168.1.255, hosts 192.168.1.1-192.168.1.254 (254 usable), mask 255.255.255.0.

Point-to-point /30

203.0.113.0/30 is a four-address block with two usable hosts - common for ISP or router links.

Host route /32

198.51.100.7/32 is a single-host route: network and broadcast are the same address, with 1 usable host.

RFC 3021 /31

10.0.0.0/31 treats both addresses as usable on a point-to-point link (no classic broadcast).

Class B private /16

172.16.5.9/16 expands to network 172.16.0.0 with 65,534 usable hosts and mask 255.255.0.0.

Common Use Cases

Size a new VLAN or office LAN from a CIDR block
Convert slash notation to a dotted subnet mask for older UIs
Find first and last usable hosts before writing DHCP pools
Check whether an IP is the network or broadcast address
Document firewall or ACL ranges from a CIDR string

Frequently Asked Questions about IP Subnet Calculator

How do I use this IP subnet calculator?: Paste an IPv4 CIDR such as 192.168.1.10/24 (or a bare IP with the prefix override). The page shows network, broadcast, host range, masks, and host counts immediately. Nothing is uploaded.
What is CIDR notation?: CIDR appends a slash and prefix length to an IP (e.g. /24). The prefix is how many leading bits belong to the network; the rest are host bits. /24 means a 255.255.255.0 mask and 256 addresses.
How are usable hosts calculated?: For prefixes shorter than /31, usable hosts = total addresses minus network and broadcast. /31 follows RFC 3021 (both addresses usable). /32 is a single host route with 1 usable address.
What is the difference between subnet mask and wildcard mask?: The subnet mask has 1-bits for the network portion (e.g. 255.255.255.0). The wildcard mask is the inverse (0.0.0.255) and appears in some ACL and OSPF configs.
Does this support IPv6?: Not yet. This tool focuses on IPv4 CIDR math - network, broadcast, host range, and masks for 0-32 prefixes.
Is my IP address uploaded?: No. All calculation runs locally in this tab. Addresses never leave your browser.
Why does /31 look different from other prefixes?: RFC 3021 allows /31 on point-to-point links so both addresses can be used as hosts. There is no classic unused broadcast address in that mode.
What does IP class mean here?: The classical A-E letter from the first octet (historical). Modern networks use CIDR, but class still appears in older docs and exams.

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