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Subnet Calculator

How to Use

  1. 1

    Enter the IP address

    Enter a valid IP address (e.g., 192.168.1.0) in the corresponding field.

  2. 2

    Select the mask

    Choose the subnet mask in CIDR notation (/24, /25, /26, etc.) or custom mask.

  3. 3

    Configure additional options

    Select whether to view the subnet table, IP ranges, and broadcast addresses.

  4. 4

    Get the results

    The tool will automatically display: network address, broadcast, decimal and CIDR mask, number of hosts, and usable IP range.

What is a subnet?

A subnet is a logical division of an IP network into smaller segments. Subnet calculation allows you to determine:

  • Network address: Identifies the entire subnet (first IP with host bits set to 0)
  • Broadcast: Special address to send data to all hosts (last IP with host bits set to 1)
  • Subnet mask: Defines which portion of an IP belongs to the network and which to the host
  • Usable IP range: Available addresses for devices on the network

CIDR (Classless Inter-Domain Routing) is a notation indicating the number of bits dedicated to the network portion. For example, /24 means 24 bits for network and 8 for host, equaling 256 addresses (254 usable).

Need subnets of different sizes? Use our VLSM Calculator to create optimized addressing plans with variable-length subnet masks.

Use this CIDR calculator to instantly determine the network address, broadcast, and usable IP range for any prefix. Unlike a basic subnet mask calculator, this IP subnet calculator includes cloud-specific presets: the AWS VPC subnet calculator mode shows the 5 reserved IPs per subnet and validates that your CIDR meets the /28 minimum — perfect for planning any cloud subnet deployment on AWS, Azure, or GCP. You also get the network address calculator output for each subnet along with a full /1 to /32 reference table. A professional subnetting tool built for network engineers, sysadmins, and cloud architects who need precision.

IPv6 Subnetting

Unlike IPv4, IPv6 doesn't use dotted-decimal subnet masks. Instead, it relies on an IPv6 prefix length — a single number after the slash that defines the network portion of the 128-bit address. The most common prefix is /64, which leaves 64 bits for host identification — enough for 18.4 trillion devices per subnet. For IPv6 address planning, the 16-bit subnet ID within a typical /48 allocation from your RIR gives you 65,536 individual /64 subnets, a scale impossible with IPv4.

Our built-in IPv6 subnet calculator lets you enter any IPv6 address and prefix to instantly get the network address, full address range, and next prefix. Whether you're migrating from IPv4 or designing a greenfield network, the IPv6 subnetting support in this tool eliminates manual hex conversion errors. Try entering 2001:db8::/32 and explore available /64 subnets.

IPv4 Subnet Table (/1 to /32)

Complete CIDR prefix table with subnet mask, total IPs and usable hosts.

CIDR Mask Total IPs Usable IPs
/1 128.0.0.0 2,147,483,648 2,147,483,646
/2 192.0.0.0 1,073,741,824 1,073,741,822
/3 224.0.0.0 536,870,912 536,870,910
/4 240.0.0.0 268,435,456 268,435,454
/5 248.0.0.0 134,217,728 134,217,726
/6 252.0.0.0 67,108,864 67,108,862
/7 254.0.0.0 33,554,432 33,554,430
/8 255.0.0.0 16,777,216 16,777,214
/9 255.128.0.0 8,388,608 8,388,606
/10 255.192.0.0 4,194,304 4,194,302
/11 255.224.0.0 2,097,152 2,097,150
/12 255.240.0.0 1,048,576 1,048,574
/13 255.248.0.0 524,288 524,286
/14 255.252.0.0 262,144 262,142
/15 255.254.0.0 131,072 131,070
/16 255.255.0.0 65,536 65,534
/17 255.255.128.0 32,768 32,766
/18 255.255.192.0 16,384 16,382
/19 255.255.224.0 8,192 8,190
/20 255.255.240.0 4,096 4,094
/21 255.255.248.0 2,048 2,046
/22 255.255.252.0 1,024 1,022
/23 255.255.254.0 512 510
/24 255.255.255.0 256 254
/25 255.255.255.128 128 126
/26 255.255.255.192 64 62
/27 255.255.255.224 32 30
/28 255.255.255.240 16 14
/29 255.255.255.248 8 6
/30 255.255.255.252 4 2
/31 255.255.255.254 2 2
/32 255.255.255.255 1 1

Highlighted rows: /8, /16, /24 — the most common prefixes in enterprise networks.

Cloud Providers: Recommended CIDR Ranges

Provider Min CIDR Max CIDR Default Reserved IPs
AWS VPC /16 /28 /16 5 per subnet
Azure VNet /8 /29 /16 5 per subnet
GCP VPC /8 /29 /16 4 per subnet

Each cloud provider reserves the first IPs of every subnet for network, gateway, DNS, and broadcast addresses. AWS and Azure reserve 5 IPs (network, VPC router, DNS, future, broadcast), while GCP reserves 4 (network, gateway, broadcast, second IP).

Network Toolkit

All the network tools you need as a sysadmin or DevOps engineer, grouped in one place.

Subnet Calculator

Free subnet calculator for IPv4 and IPv6 — get network address, CIDR mask, IP range, and cloud provider presets.

VLSM Calculator

Variable Length Subnet Mask calculator for optimized IP addressing plans with automatic subnet allocation.

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SNMP OID Translator

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BDP Calculator

Compute Bandwidth-Delay Product to tune TCP window sizes for high-latency or high-bandwidth links.

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Convert between storage units — bytes, KiB, MiB, GiB, TiB — in both decimal and binary notation.

Umask Calculator

Calculate umask values and the resulting file and directory permissions on Linux/Unix systems.

Frequently Asked Questions

What is a subnet and what is it for?
A subnet is a logical division of an IP network into smaller segments. It improves addressing efficiency, reduces broadcast traffic, enhances security by isolating network segments, and simplifies administration by organizing devices by departments or functions within an organization.

What is a subnet mask?
A subnet mask is a 32-bit number that determines which portion of an IP address belongs to the network and which belongs to the host. For example, the mask 255.255.255.0 (/24) indicates the first 24 bits are the network and the last 8 bits are for hosts, allowing 254 usable addresses.

What is the difference between IPv4 and IPv6 subnetting?
IPv4 uses 32-bit subnet masks in decimal or CIDR notation, while IPv6 uses 128-bit prefixes without a traditional subnet mask. IPv6 dedicates 16 bits specifically for subnetting, allowing 65,536 subnets per prefix, compared to IPv4 where each additional subnet bit reduces available hosts.

How to calculate a subnet manually?
To calculate a subnet manually: 1) Convert the IP and mask to binary, 2) Apply a logical AND between IP and mask to get the network address, 3) Set all host bits to 1 for the broadcast address, 4) The usable range is from network+1 to broadcast-1. A subnet calculator automates this entire process.
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