What's the difference between a subnet calculator and a CIDR calculator?

CIDR notation is the /prefix form of a subnet mask, such as /24 for 255.255.255.0. This tool takes either an IPv4 address in CIDR notation or a prefix length and shows the network address, broadcast address, usable host range, and host count. It runs locally in your browser, and nothing is uploaded.

Does this subnet calculator send my IP addresses to a server?

No. All IP parsing and subnet bitwise arithmetic execute locally in JavaScript inside your browser. No IP addresses, subnets, or network topologies are ever transmitted or logged.

What is CIDR notation?

Classless Inter-Domain Routing (CIDR) notation expresses an IP address and its associated routing prefix length using a forward slash followed by the count of leading 1 bits in the subnet mask (e.g. /24 equals 255.255.255.0).

How are usable host addresses determined?

For standard subnets (/0 to /30), the first address is the Network Address and the last address is the Broadcast Address, leaving 2^(32 - prefix) - 2 usable host addresses. For point-to-point links (/31 under RFC 3021), both addresses are usable hosts. For /32 host routes, 1 host is addressable.

What is a wildcard mask?

A wildcard mask is the bitwise inverse of a subnet mask (255.255.255.255 - subnet mask). It is commonly used in Cisco IOS Access Control Lists (ACLs) and Open Shortest Path First (OSPF) network configurations.

How do I calculate an IPv4 subnet without this page?

Convert the 4 octets to a 32-bit integer: ipInt = (o1 >> 0. Wildcard mask = (~maskInt) >>> 0. Network address = (ipInt & maskInt) >>> 0. Broadcast address = (networkInt | wildcardInt) >>> 0. Total hosts = 2^(32 - n). Usable hosts = n === 32 ? 1 : n === 31 ? 2 : Math.max(0, totalHosts - 2). First usable = networkInt + 1; last usable = broadcastInt - 1. Format each 32-bit int as octets: (int >>> 24) & 255, (int >>> 16) & 255, (int >>> 8) & 255, int & 255.

Subnet calculator

Enter an IPv4 address and CIDR prefix length (or standard subnet mask) to calculate network boundaries, broadcast addresses, usable host ranges, and wildcard masks. Includes bit breakdown and quick prefix reference. All math runs entirely in this browser tab without network requests.

Runs locally in your browser · No network requests

Presets:

IP Address (or CIDR)

Supports standard IPv4 or CIDR format like 10.0.0.1/24

Subnet Mask / Prefix

/24 (255.255.255.0)

Quick Prefix Slider:/24 (255.255.255.0)

/0 (Internet)/8 (Class A)/16 (Class B)/24 (Class C)/32 (Host)

Calculation Results

Network Address

192.168.1.0

/24

Subnet Mask

255.255.255.0

Wildcard: 0.0.0.255

Usable Hosts

254

Total: 256

Broadcast Address

192.168.1.255

Scope: Private

Network & Addressing Specification

Usable Host Range: 192.168.1.1 – 192.168.1.254
First Usable Host: 192.168.1.1
Last Usable Host: 192.168.1.254
CIDR Notation: 192.168.1.0/24
IP Classification: Class C · Private (RFC 1918)
Hex Representation: IP: 0xc0a80132 · Mask: 0xffffff00

Binary Bit Breakdown

IP Address:11000000.10101000.00000001.00110010

Subnet Mask:11111111.11111111.11111111.00000000

Network ID:11000000.10101000.00000001.00000000

Broadcast:11000000.10101000.00000001.11111111

Subnet mask has 24 network bits and 8 host bits.

Common IPv4 CIDR Reference Table

CIDR	Subnet Mask	Usable Hosts	Common Usage
/8	255.0.0.0	16,777,214	Class A (/8)
/16	255.255.0.0	65,534	Class B (/16)
/20	255.255.240.0	4,094	Large Office (/20)
/22	255.255.252.0	1,022	Medium Office (/22)
/24	255.255.255.0	254	Class C / Standard LAN (/24)
/25	255.255.255.128	126	Half Subnet (/25)
/26	255.255.255.192	62	Quarter Subnet (/26)
/27	255.255.255.224	30	32-IP Block (/27)
/28	255.255.255.240	14	16-IP Block (/28)
/29	255.255.255.248	6	Small Subnet (/29)
/30	255.255.255.252	2	Legacy Point-to-Point (/30)
/31	255.255.255.254	2	Modern Point-to-Point (/31)
/32	255.255.255.255	1	Host Route (/32)