IP Calculator
Calculate IPv4 subnets, host ranges, address details, and narrower subnet splits.
IPv4 with an optional /0–/32 prefix. All calculations stay in this browser.
192.168.1.0192.168.1.255255.255.255.00.0.0.255192.168.1.0/24192.168.1.1192.168.1.254256254Working notes
Use IP Calculator with the boundary visible.
IP Calculator derives IPv4 subnet boundaries, masks, usable host ranges, address classification, numeric forms, and narrower subnet ranges entirely in your browser.
What is IP Calculator?
Every device on an IP network needs a unique address and a way to know which other addresses are on the same local network versus a remote one. Subnetting divides an IP address into a network portion and a host portion using a subnet mask. CIDR (Classless Inter-Domain Routing) notation expresses this compactly: 192.168.1.0/24 means the first 24 bits identify the network (192.168.1) and the remaining 8 bits identify hosts (0-255), giving 256 total addresses and 254 usable hosts (the first is the network address and the last is the broadcast address). Understanding subnetting is essential for designing network architectures, configuring firewalls and security groups, planning VPC layouts in cloud environments, and troubleshooting connectivity. A subnet calculator takes a CIDR block and instantly derives the network address, broadcast address, subnet mask, wildcard mask, usable host range, total address count, and address classification (Class A/B/C, private/public). The split function divides a network into smaller subnets — for example, splitting a /24 into four /26 networks of 62 hosts each — which is the core task when planning VLANs, cloud subnets, or office network segments.
When to use it
- Planning cloud VPCs — calculate how many hosts fit in a /20 or /24 subnet before creating AWS VPCs, Azure VNets, or GCP subnets.
- Configuring firewall rules — determine the exact CIDR range to allow or deny in security group rules and ACLs.
- Designing office networks — split a /16 allocation into /24 subnets for different floors, departments, or VLANs.
- Troubleshooting connectivity — check whether two IP addresses are on the same subnet or require routing through a gateway.
- IP address management (IPAM) — verify that a new allocation does not overlap with existing subnets and has enough usable host addresses.
How to use it
- 01Enter an IPv4 address with an optional CIDR prefix (e.g., 192.168.1.42/24), or choose the prefix with the slider.
- 02Review the computed results: network address, broadcast address, subnet mask, wildcard mask, usable host range, total addresses, and address classification.
- 03Inspect additional representations: the IP address as a 32-bit integer, hexadecimal, and binary.
- 04To split the network, open Split, choose a narrower prefix, and inspect the resulting subnet ranges with their network, broadcast, and host counts.
- 05For very large splits, the tool computes the full count but displays up to the first 256 subnet ranges.
Common mistakes
- Forgetting to subtract network and broadcast addresses — a /24 has 256 total addresses but only 254 usable hosts. A /30 has 4 addresses but only 2 usable hosts (common for point-to-point links).
- Confusing subnet mask and wildcard mask — the subnet mask (e.g., 255.255.255.0) identifies the network portion. The wildcard mask (0.0.0.255) is its bitwise inverse, used in ACLs and OSPF configuration.
- Overlapping subnets — when splitting a network, ensure that new subnets do not overlap with existing allocations. Two overlapping ranges on the same network cause routing ambiguity.
- Using classful thinking — the old Class A/B/C designations are informational only. Modern networks use CIDR, where any prefix length is valid. A /20 is not "part of a Class A" — it is simply a 4,096-address block.
- Ignoring reserved ranges — 10.0.0.0/8, 172.16.0.0/12, and 192.168.0.0/16 are private (RFC 1918). 127.0.0.0/8 is loopback. 169.254.0.0/16 is link-local. Do not route these on the public internet.
Synthetic example
Inspect a private /24 network
Input
192.168.1.42/24
Result
Network 192.168.1.0 · broadcast 192.168.1.255 · 254 usable hosts
Common subnet sizes
| Feature | /24 | /20 | /16 | /8 |
|---|---|---|---|---|
| Total addresses | 256 | 4,096 | 65,536 | 16,777,216 |
| Usable hosts | 254 | 4,094 | 65,534 | 16,777,214 |
| Subnet mask | 255.255.255.0 | 255.255.240.0 | 255.255.0.0 | 255.0.0.0 |
| Typical use | Small LAN, VLAN | Cloud VPC | Campus network | Large ISP block |
| Splits into /24s | 1 | 16 | 256 | 65,536 |
Related standards
Limits and data boundary
- IPv4 is supported; IPv6 calculation is not included.
- Classful labels are informational and do not replace CIDR routing.
- Very large splits report the full count but display only the first 256 subnet ranges.
Frequently asked questions
- What is CIDR notation?
- CIDR (Classless Inter-Domain Routing) notation appends a prefix length to an IP address (e.g., 192.168.1.0/24) to define the network size. The prefix length indicates how many bits identify the network.
- How many usable hosts does a /24 subnet have?
- A /24 subnet has 256 total addresses, but the first (network) and last (broadcast) are reserved, leaving 254 usable host addresses.
- Does this tool support IPv6?
- No. This calculator covers IPv4 subnets, masks, host ranges, and CIDR splits. IPv6 calculation is not included in this version.
- What is subnet splitting?
- Subnet splitting divides a network into smaller subnets. Choose a narrower prefix than the original to see the resulting subnet ranges, their network and broadcast addresses, and host counts.
- What is the difference between subnet mask and wildcard mask?
- A subnet mask (e.g., 255.255.255.0) marks network bits with 1s and host bits with 0s. A wildcard mask (0.0.0.255) is the bitwise inverse, used in Cisco ACLs and OSPF to match host bits.
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