What is a subnet mask?

A subnet mask is a 32-bit number that divides an IP address into network and host portions. For example, /24 corresponds to a subnet mask of 255.255.255.0.

What does CIDR notation mean?

CIDR (Classless Inter-Domain Routing) notation expresses an IP address and its subnet mask together, e.g., 192.168.1.0/24, where /24 means the first 24 bits are the network portion.

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IP Subnet Calculator

Calculate IPv4 and IPv6 subnet information including network address, usable host range, broadcast address, subnet mask, wildcard mask, CIDR notation, and more. Also lists all possible subnets for a given prefix.

IPv4IPv6CIDRSubnet MaskNetwork AddressHost Range

How to use this calculator
Select a Network Class and Subnet mask, then enter an IP address. Click Calculate to see full subnet details and all possible networks for that prefix. For IPv6, select a Prefix Length and enter an IPv6 address.

IPv4 Subnet Calculator

Enter IP address and subnet mask

Network Class

AnyClass AClass BClass C

Subnet

IP Address

IPv6 Subnet Calculator

Enter IPv6 address and prefix length

Prefix Length

IP Address

About IP Subnetting

A subnet is a logical subdivision of an IP network. Subnetting divides a large network into smaller, more manageable segments, improving performance and security. The process is governed by a subnet mask (IPv4) or prefix length (IPv6), which determines which portion of an IP address identifies the network and which identifies the host.

CIDR (Classless Inter-Domain Routing) notation expresses both the IP address and its associated routing prefix — for example, 192.168.1.0/24 means the first 24 bits are the network portion, leaving 8 bits for host addresses (254 usable hosts).

IPv4 addresses are 32-bit numbers divided into four octets. IPv6 addresses are 128-bit numbers, providing a vastly larger address space (approximately 3.4 × 10³⁸ addresses) to accommodate the growing number of internet-connected devices.

IPv4 Subnet Reference Table

Prefix Size	Network Mask	Usable Hosts / Subnet
/1	128.0.0.0	2,147,483,646
/2	192.0.0.0	1,073,741,822
/3	224.0.0.0	536,870,910
/4	240.0.0.0	268,435,454
/5	248.0.0.0	134,217,726
/6	252.0.0.0	67,108,862
/7	254.0.0.0	33,554,430
Class A
/8	255.0.0.0	16,777,214
/9	255.128.0.0	8,388,606
/10	255.192.0.0	4,194,302
/11	255.224.0.0	2,097,150
/12	255.240.0.0	1,048,574
/13	255.248.0.0	524,286
/14	255.252.0.0	262,142
/15	255.254.0.0	131,070
Class B
/16	255.255.0.0	65,534
/17	255.255.128.0	32,766
/18	255.255.192.0	16,382
/19	255.255.224.0	8,190
/20	255.255.240.0	4,094
/21	255.255.248.0	2,046
/22	255.255.252.0	1,022
/23	255.255.254.0	510
Class C
/24	255.255.255.0	254
/25	255.255.255.128	126
/26	255.255.255.192	62
/27	255.255.255.224	30
/28	255.255.255.240	14
/29	255.255.255.248	6
/30	255.255.255.252	2
/31	255.255.255.254	0
/32	255.255.255.255	0

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Quick Reference

• /24 = 254 usable hosts (Class C)
• /16 = 65,534 usable hosts (Class B)
• /8 = 16,777,214 usable hosts (Class A)
• /32 = single host (no subnet)
• /30 = 2 usable hosts (point-to-point)
• Private: 10.x, 172.16–31.x, 192.168.x
• Loopback: 127.0.0.1

Common Subnets

/24255.255.255.0254 hosts

/25255.255.255.128126 hosts

/26255.255.255.19262 hosts

/27255.255.255.22430 hosts

/28255.255.255.24014 hosts

/29255.255.255.2486 hosts

/30255.255.255.2522 hosts

In-Depth Guide

This calculator provides quick and accurate results for your calculations. Simply enter your values and get instant results.

The calculation uses standard formulas and methods to ensure accuracy. All inputs are validated to prevent errors.

Use this tool to save time and avoid manual calculation errors. Results are displayed clearly for easy interpretation.

Tips & Considerations

→Double-check your input values before calculating to ensure accurate results.
→Use the calculator regularly to track changes over time.
→Compare results with different input values to understand the impact of each variable.
→Consult a professional for important financial or health decisions.
→Bookmark this page for quick access whenever you need to calculate.

Frequently Asked Questions

This calculator uses standard formulas and methods to provide accurate results. However, results are estimates and should be verified with a professional for important decisions.