ITBox
Switch tool

IP Calculator

IPv4 + mask / CIDR → network, broadcast, usable hosts.

Accepts CIDR (e.g. 192.168.1.0/24), a /N prefix, or dotted mask (255.255.255.0).

How to use

Purpose

Online IP/subnet calculator. From CIDR (192.168.1.0/24) computes network address, broadcast address, subnet mask, usable host count, IP range, binary representation. Supports subnetting (VLSM), supernetting (combine multiple subnets), IPv4/IPv6. Recognizes IP type (Class A/B/C/D/E, private, reserved). All computation runs locally.

Steps

  1. Type IP + CIDR prefix (e.g. 192.168.1.0/24)
  2. Tool outputs network address, broadcast, subnet mask, usable hosts, IP range
  3. Binary view: 32 bits split into binary
  4. Reverse: input subnet mask + any IP, get CIDR
  5. Subnetting: split /24 into 4 /26, list IP range of each
  6. Supernetting: input several subnets, get smallest covering CIDR
  7. IPv6 mode: ::1, fe80::/10, etc.
  8. Type detection: private/public/reserved

FAQ

How many usable IPs in /24?
/24 has 256 IPs total (256 = 2^8, first 24 bits network, 8 bits host). Usable hosts = 256 - 2 = 254 (subtract network .0 and broadcast .255). Small subnet /30: 4 IPs, 2 usable (point-to-point links). Single /32: 1 IP (precise routing).
What is a private IP?
RFC 1918 defines three private ranges: 10.0.0.0/8 (Class A, large enterprises), 172.16.0.0/12 (Class B, mid-size), 192.168.0.0/16 (Class C, home routers default). Private IPs are not routable on the public Internet; multiple networks can use the same range. Internet traffic goes through NAT to a public IP.
Subnet mask 255.255.255.0 = which CIDR?
255.255.255.0 binary = 24 ones + 8 zeros, CIDR /24. Common: /8 = 255.0.0.0, /16 = 255.255.0.0, /24 = 255.255.255.0, /30 = 255.255.255.252. Tool converts CIDR ↔ mask both ways.
How to read IPv6?
IPv6 is 128 bits (IPv4 is 32). Eight groups of 4 hex digits separated by :. Example: 2001:0db8:85a3:0000:0000:8a2e:0370:7334. Simplification: 1) leading zeros omitted (0db8 → db8); 2) consecutive all-zero groups → :: (once per address). Simplified: 2001:db8:85a3::8a2e:370:7334. Link-local: fe80::; loopback: ::1.
Is CIDR /23 larger or smaller than /24?
Shorter prefix = larger subnet. /23 (22 bits network) has 2^9 = 512 IPs (510 usable). /24 (24 bits) has 256 (254 usable). /23 is twice as large. Memory aid: /16 ≈ 65K IPs, /24 = 256, /32 = 1.

Use cases

  • Network planning: subnet division for new office, allocating per department
  • Routing triage: reverse subnet range from routing table CIDR
  • Security config: firewall rules with CIDR allowlists
  • Cloud VPC: AWS / Aliyun / GCP VPC subnet design
  • Ops training: teach subnet division to newcomers

Use cases

Enterprise network planning, routing triage, firewall rules, cloud VPC design, network teaching. Network engineer, SRE, ops, cloud architect. Subnetting, supernetting, IPv6, type detection, binary view are the differentiators.