Skip to main content

IP Subnet Calculator

Enter a valid IPv4 address such as 10.0.0.1 or 192.168.1.10. This calculator currently supports IPv4.

Choose a prefix from 0 to 32. For example, /24 equals the subnet mask 255.255.255.0.

Check this to include binary representations of the IP, subnet mask, network, and broadcast.

Tip: If you are unsure of the correct CIDR, common values are /24 (255.255.255.0), /23 (255.255.254.0), and /16 (255.255.0.0).

No data is stored. Your inputs are used only to calculate results on the server.

IP Subnet Calculator

Use our fast, accurate IP Subnet Calculator to derive network address, broadcast address, host range, usable hosts, and more from any IPv4 address and CIDR prefix.

What is an IP Subnet Calculator?

An IP Subnet Calculator is a networking utility that performs all the essential subnetting math instantly. By entering an IPv4 address and a CIDR prefix length (for example, 192.168.1.10 with /24), you can immediately see the network address, broadcast address, first and last usable host, total addresses, and usable host count. This saves time, reduces human error, and helps administrators plan networks, allocate IP ranges, and troubleshoot connectivity issues efficiently.

Why use this IP Subnet Calculator?

  • Instant results: Convert IP and CIDR to a full set of subnet details in milliseconds.
  • Accurate planning: Confidently size subnets, check host capacity, and validate address boundaries.
  • Error reduction: Avoid manual arithmetic mistakes when calculating masks and ranges.
  • Readable output: Clearly labeled network, broadcast, hosts, and optional binary breakdowns.

How to use the calculator

  1. Enter a valid IPv4 address (e.g., 10.0.5.17).
  2. Specify the CIDR prefix length (0–32). For example, /24 equals 255.255.255.0.
  3. Optionally check “Show binary details” to display binary forms of critical values.
  4. Click “Calculate Subnet” to view results, including host range and counts.

What the results mean

  • Network address: The first address in the subnet; identifies the subnet itself.
  • Broadcast address: The last address; used to reach all hosts in the subnet (traditional IPv4).
  • First and last usable host: The range of assignable addresses for devices. For most subnets, these exclude the network and broadcast addresses. Special cases like /31 and /32 follow modern conventions.
  • Subnet mask and wildcard mask: The dotted-decimal mask and its inverse, often used in ACLs.
  • Total and usable addresses: The total count in the subnet and how many can typically be assigned.

Common CIDR examples

  • /30: 4 total addresses, typically 2 usable; ideal for point-to-point links (traditional).
  • /29: 8 total, 6 usable; small device clusters.
  • /24: 256 total, 254 usable; common LAN subnet.
  • /16: 65,536 total, 65,534 usable; large internal networks.

Best practices for subnetting

  • Right-size subnets to match host counts and growth expectations.
  • Keep related services within the same subnet to simplify ACLs and routing.
  • Document allocations and reserve ranges for infrastructure devices.
  • Leverage private address space (10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16) for internal networks.

When to check binary output

Binary output helps visualize how the subnet mask splits network and host bits. This is especially useful when teaching subnetting or when diagnosing edge cases like overlapping subnets. Seeing the bitwise relationship between an IP and its mask can make troubleshooting route summaries, ACLs, and NAT scenarios more intuitive.

Troubleshooting tips

  • If the host count seems off, verify the CIDR prefix and remember special cases like /31 and /32.
  • Ensure the IP address is in the expected private or public range for your use case.
  • Check for overlapping subnets that may cause routing or DHCP conflicts.

Whether you are planning a new VLAN, carving out point-to-point links, or validating an address assignment, this IP Subnet Calculator delivers the clarity and precision you need to get the job done right.

FAQs

What does the IP Subnet Calculator show after I enter an IP and CIDR?

It displays the network and broadcast addresses, host range, usable hosts, subnet mask, wildcard mask, and more.

How do I choose the right CIDR in the IP Subnet Calculator?

Estimate how many hosts you need. For example, /24 fits up to 254 usable hosts; /29 fits 6 usable hosts.

Can the IP Subnet Calculator handle /31 and /32 networks?

Yes. It treats /31 as point-to-point (2 usable) and /32 as a single-address host route.

Does the IP Subnet Calculator support private IP ranges?

Yes. It identifies whether the entered IP falls into private ranges like 10/8, 172.16/12, or 192.168/16.

Why would I enable binary output in the IP Subnet Calculator?

Binary output helps visualize how the mask splits network and host bits, useful for learning and troubleshooting.

Is the IP Subnet Calculator suitable for network planning?

Absolutely. It helps size subnets, avoid overlaps, and validate address assignments before deployment.

Does the IP Subnet Calculator store my IP data?

No. Inputs are used only to compute results and are not stored.

Can I use the IP Subnet Calculator to find the wildcard mask for ACLs?

Yes. The results include the wildcard mask, which is the inverse of the subnet mask.