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Overview

IPv4 CIDR Calculator

Calculate the subnet boundary for one IPv4 CIDR block, including mask, broadcast, wildcard, and usable host range without leaving the browser.

What isHow to useExampleCommon use casesFrequently asked questions

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#broadcast-address-finder#wildcard-mask-calculator#ipv4-subnet-calculator#subnet-mask-calculator#ip-networking-tool
IPv4 Networking

IPv4 CIDR Calculator

Parse one IPv4 CIDR block and surface the exact subnet boundary, mask, broadcast address, and usable host range.

Network
192.168.1.32
Broadcast
192.168.1.63
Subnet mask
255.255.255.224
Wildcard mask
0.0.0.31
Usable hosts
30
Total addresses
32
Host range
First host
192.168.1.33
Last host
192.168.1.62
Binary view
Octet 1: 11000000
Octet 2: 10101000
Octet 3: 00000001
Octet 4: 00101010

`/31` and `/32` blocks are displayed without a usable-host range because they are commonly treated as point-to-point or single-address allocations.

What you can solve

How do I find the network address from an IPv4 CIDR block?

Take the IPv4 address, apply the subnet mask implied by the prefix length, and zero the host bits. For example, a `/27` prefix means `255.255.255.224`, so `192.168.1.42/27` falls into the `192.168.1.32` network. A calculator is useful because it removes the need to convert octets and bit boundaries manually every time.

What is the difference between the broadcast address and the last usable host?

The broadcast address is the highest address in the subnet and is traditionally reserved for sending traffic to every host on that network segment. The last usable host is one address lower, because it is the highest address that can usually be assigned to a device in standard IPv4 subnetting.

Why would I care about the wildcard mask?

Wildcard masks still appear in router ACLs, older firewall interfaces, and network exam material. They represent the inverse of the subnet mask, so seeing both values together helps when you need to translate a CIDR block into a rule format that does not accept prefix notation directly.

How do I calculate how many usable hosts are in a CIDR block?

The total address count is 2^(32 - prefix length). Subtract 2 for the network address and broadcast address to get usable hosts. A /24 block gives 256 total addresses and 254 usable hosts, while a /30 gives 4 total and 2 usable — useful for point-to-point links. The calculator shows both totals so you can pick the right prefix for your host requirements.

How do I check whether an IP address belongs to a given CIDR subnet?

Apply the subnet mask to both the IP address and the network address using a bitwise AND. If both results are equal, the IP is within the subnet. For example, 192.168.1.50 ANDed with a /24 mask (255.255.255.0) gives 192.168.1.0, which matches the network address. Enter the CIDR block and compare the shown range against your target IP.

Typical workflow

URL Query Parameter InspectorIPv4 CIDR CalculatorHTTP Status Code Explorer

Guides for this workflow

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What is

What is IPv4 CIDR Calculator?

An IPv4 CIDR calculator helps you stop guessing at subnet boundaries when you only have an address like `192.168.1.42/27`. Instead of mentally converting octets or reaching for a CLI every time, you can paste one CIDR block and immediately see the network address, subnet mask, wildcard mask, broadcast address, and practical host range.

This is useful during firewall reviews, reverse-proxy setup, internal network planning, and cloud security group work where one off-by-one assumption can put the wrong machines in scope.

How to use

How to use IPv4 CIDR Calculator

Paste one IPv4 address with a prefix length such as `10.0.0.15/8` or `203.0.113.9/30`. The calculator validates the CIDR string, computes the exact subnet boundary, and shows the host range and address counts. Use the preset examples when you want a quick sanity check before entering your own block.

Example

Example

Example:
Input: `192.168.1.42/27`

The tool calculates:
1. Network address: `192.168.1.32`
2. Broadcast address: `192.168.1.63`
3. Subnet mask: `255.255.255.224`
4. Usable host range: `192.168.1.33` to `192.168.1.62`
5. Usable hosts: `30`

Common use cases

Common use cases

1. Checking whether an application server and a gateway belong to the same subnet.

2. Verifying a firewall rule before entering source and destination CIDR blocks.

3. Confirming broadcast and wildcard values for legacy network hardware or ACL input.

4. Explaining subnet boundaries to teammates during infrastructure review.

Frequently asked questions

Frequently asked questions

What does this CIDR calculator show beyond a subnet mask?v
It surfaces the network address, broadcast address, wildcard mask, total address count, usable host count, and first and last host addresses so you can reason about the full allocation instead of just the mask.
Why do /31 and /32 blocks show zero usable hosts?v
This tool treats them conservatively because many engineers still think in terms of classic host ranges where network and broadcast addresses are reserved. The boundary values are still shown so you can inspect the allocation directly.
Does this tool support IPv6?v
No. It is intentionally scoped to one job: inspecting IPv4 CIDR math clearly and quickly. IPv6 should be handled by a separate focused tool.