How many usable hosts are in a /26 or /30 subnet?

A /26 has 62 usable hosts and a /30 has 2. For any prefix from /0 to /30, the usable host count is the total addresses minus two, because the first address is the network and the last is the broadcast. A /24 has 254 usable hosts, a /26 has 62, and a /30 has 2.

How do I calculate the network and broadcast address from a CIDR prefix?

AND the address with the subnet mask to get the network address, then set every host bit to one to get the broadcast address. For 192.168.10.77/26 the mask is 255.255.255.192, so the network address is 192.168.10.64 and the broadcast address is 192.168.10.127. The network address identifies the subnet itself, and the broadcast address reaches every host on the subnet at once.

How do I convert a subnet mask to a CIDR prefix?

Count the leading one-bits in the mask. 255.255.255.0 is 24 one-bits, so it is /24; 255.255.240.0 is 20 bits, so /20. This calculator does the conversion for you when you enter a dotted mask instead of a prefix.

What is a wildcard mask used for in access control lists?

A wildcard mask tells an access control list which bits of an address to match, and it is the bit-inverse of the subnet mask, so /24 gives 0.0.0.255 and /26 gives 0.0.0.63. It is used in Cisco access control lists and OSPF network statements, where a zero bit means match exactly and a one bit means ignore that bit.

Does this calculator handle a /31 point-to-point link correctly?

Yes, a /31 shows 2 usable hosts, not 0. For 198.51.100.8/31 the usable host range is 198.51.100.8 - 198.51.100.9. RFC 3021 lets a /31 be used on point-to-point links where the network and broadcast addresses are not needed, so both of its two addresses become usable host addresses. A /32 represents a single host, such as a loopback or a host route.

Which address ranges are private?

RFC 1918 reserves 10.0.0.0/8, 172.16.0.0/12, and 192.168.0.0/16 for private networks. These are not routable on the public internet and are the ranges most home and office networks use behind a router doing NAT.

Why does 100.64.0.1 show as Public?

The Type row checks only the three RFC 1918 ranges, so every other address reads Public. Carrier-grade NAT space (100.64.0.0/10, RFC 6598), link-local addresses (169.254.0.0/16) and loopback (127.0.0.0/8) are not routable on the internet either, but this calculator labels them Public. The network, broadcast and host range figures for those addresses are still correct.

Does the IP subnet calculator show a default gateway?

No, there is no gateway field, because a subnet does not define one: the gateway is whatever address you assign to the router. By common convention it is the first usable host, so for 192.168.10.77/26 you would read 192.168.10.65 from the start of the Usable host range row. Some networks use the last usable host instead, 192.168.10.126 in that example.

Does this subnet calculator work for IPv6?

No, this tool calculates IPv4 subnets only. IPv6 uses 128-bit addresses and different notation, so its subnetting is handled differently. For IPv4 planning, firewall rules, and VPC sizing, this covers the common cases.

IP Subnet Calculator

Calculate the network address, broadcast, usable host range, subnet mask, and host count for any IPv4 address and CIDR prefix.

IP address and prefix

Common prefixes

CIDR	Subnet mask	Addresses	Usable hosts
/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

Category:web

Mode:Offline

Version:1.0.0

Access:Free

What is an IP subnet calculator?

An IP subnet calculator takes an IPv4 address and a CIDR prefix, such as 192.168.1.10/24, and works out every property of the network that address belongs to. It returns the network address, the broadcast address, the first and last usable host, the subnet mask in dotted-decimal form, the wildcard mask, and the number of total and usable addresses. Instead of doing binary arithmetic by hand, you paste one value and read the answer. The tool also accepts a dotted subnet mask in place of the prefix, so 192.168.1.10 255.255.255.0 gives the same result as /24.

Subnetting is the practice of splitting one IP address block into smaller networks. The CIDR prefix, the number after the slash, says how many bits of the address identify the network rather than the host. A /24 fixes the first 24 bits, leaving 8 bits for hosts, which is 256 addresses and 254 usable ones once the network and broadcast addresses are set aside. A smaller prefix such as /16 covers far more addresses; a larger one such as /30 leaves room for only two hosts, which is why point-to-point links use it. Getting the prefix wrong is a common source of connectivity bugs, and seeing the ranges spelled out makes the mistake obvious.

A worked example shows what this online IP subnet calculator returns. Type 192.168.10.77/26 and Subnet details fill in as you type: CIDR notation 192.168.10.64/26, network address 192.168.10.64, broadcast address 192.168.10.127, usable host range 192.168.10.65 - 192.168.10.126, subnet mask 255.255.255.192, wildcard mask 0.0.0.63, 64 total addresses and 62 usable hosts. Enter a bare address such as 10.20.30.40 with no prefix and the calculator assumes /24, so check the CIDR notation row before you copy anything.

Network engineers, system administrators, and developers reach for this constantly: planning an address scheme, writing a firewall or routing rule, sizing a cloud VPC subnet, or checking whether two hosts share a network. The calculator handles the edge cases correctly, treating a /31 as a two-host point-to-point link per RFC 3021 and a /32 as a single host. Everything runs client-side, so no address you enter is uploaded or logged, and the tool keeps working offline once the page has loaded. It is free, no signup.

How to use the IP subnet calculator?

Enter an address and prefix

Type an IPv4 address with a CIDR prefix, such as 10.0.0.0/8, in the IP address and prefix field, or click one of the sample subnets. An address with no prefix is treated as /24.

Or use a subnet mask

A dotted mask works too: enter 192.168.1.10 255.255.255.0 and the tool converts it to the matching prefix.

Read the results

Subnet details update as you type: the network and broadcast addresses, the usable host range, the mask, wildcard mask, and address counts, with a binary view of the address and mask below.

Copy what you need

Copy the CIDR notation, the host range, or the mask to drop into router configs, firewall rules, or documentation.

Key Features

Full network breakdown

Network address, broadcast address, first and last usable host, and the total and usable address counts in one view.

CIDR and dotted mask input

Accepts /24 style prefixes or dotted subnet masks like 255.255.255.0, and converts between the two.

Wildcard mask

Shows the inverse mask used in access control lists and OSPF area statements, not just the subnet mask.

Correct edge cases

Handles /31 as a two-host point-to-point link per RFC 3021 and /32 as a single host, where naive tools miscount.

Frequently Asked Questions

The CIDR prefix is the number after the slash, and it counts how many leading bits of the address identify the network. A /24 fixes the first 24 bits for the network and leaves 8 bits for hosts, which is 256 total addresses and 254 usable ones.

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Read the full IP Subnet Calculator guide

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