SysAdmin Tools

Subnet Calculator

Calculate the network address, broadcast address, subnet mask, wildcard mask, usable host range and more from any IP and CIDR prefix — instantly, in your browser.

Input as:

Quick CIDR presets

Subnet details192.168.1.0/24
IP Address192.168.1.0
Network Address192.168.1.0
Broadcast Address192.168.1.255
Subnet Mask255.255.255.0
Wildcard Mask0.0.0.255
Total Hosts256
Usable Hosts254
CIDR Notation192.168.1.0/24
Usable IP Range192.168.1.1 – 192.168.1.254
IP ClassC

Binary representation

11000000.10101000.00000001.00000000
Network bits (24) Host bits (8)

Split this network into subnets

4 subnets of /26 (62 usable hosts each)

#SubnetUsable RangeBroadcastHosts
1192.168.1.0/26192.168.1.1 – 192.168.1.62192.168.1.6362
2192.168.1.64/26192.168.1.65 – 192.168.1.126192.168.1.12762
3192.168.1.128/26192.168.1.129 – 192.168.1.190192.168.1.19162
4192.168.1.192/26192.168.1.193 – 192.168.1.254192.168.1.25562

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A subnet calculator takes an IP address and a CIDR prefix (or subnet mask) and instantly works out every value you need to plan or troubleshoot a network — the network address, broadcast address, subnet mask, wildcard mask, usable host range, and total host count. Instead of doing binary maths by hand, you get the full breakdown the moment you type an address.

This CIDR calculator runs entirely in your browser. Nothing is sent to a server, so it works offline and there is no rate limiting — ideal for firewall rule planning, ACL design, DHCP scope sizing, or studying for a networking certification. Enter an address like 192.168.1.0, choose a prefix such as /24, and the tool derives the network and broadcast address, both mask forms, and the exact list of assignable hosts.

CIDR notation and subnet masks are two ways of expressing the same thing: how many bits identify the network versus the host. This IP subnet calculator lets you switch between them — type /26 or 255.255.255.192 and see the results update either way. A colour-coded binary view shows exactly where the network boundary falls, which makes the relationship between the prefix length and the address space obvious at a glance.

The built-in network calculator also splits a block into equal subnets. Tell it how many subnets you need and it borrows the right number of host bits, then lists every resulting subnet with its own range and usable host count — the fastest way to carve a supernet into VLANs or departmental segments.

How to Use the Subnet Calculator

  1. 1

    Enter an IP address

    Type any IPv4 address in dotted-decimal form, for example 192.168.1.0 or 10.0.0.0. The tool validates each octet as you go and flags anything outside the 0–255 range.

  2. 2

    Choose a prefix or subnet mask

    Switch between CIDR mode and subnet-mask mode with the toggle. Enter a prefix such as /24, or a dotted mask such as 255.255.255.0 — both describe the same network boundary and produce identical results.

  3. 3

    Use a quick preset (optional)

    Click a preset pill — /8, /16, /24, /25, /26, /27, /28, /30 or /32 — to jump straight to a common prefix without typing. The results recalculate instantly.

  4. 4

    Read the full breakdown

    The results card shows the network and broadcast addresses, subnet and wildcard masks, total and usable hosts, the usable IP range, the IP class, and a colour-coded binary view marking the network/host boundary.

  5. 5

    Split the network into subnets

    In the subnet divider below the results, enter how many subnets you need. The tool borrows the fewest host bits required and lists every resulting subnet with its own range and usable host count.

Understanding Subnet Calculator Results

Every result comes from a single idea: the CIDR prefix marks how many leading bits of the 32-bit address identify the network, leaving the remaining bits to identify hosts. A /24 reserves 24 bits for the network and 8 for hosts, which is why it holds 256 addresses (28) with 254 usable. The network address is the first address in the block — every host bit set to 0 — and identifies the subnet itself. The broadcast address is the last address — every host bit set to 1 — and reaches every host on the segment. Because these two are reserved, the usable hosts count is normally the total minus 2. The /31 and /32 prefixes are special cases: a /31 is a two-host point-to-point link (RFC 3021) and a /32 identifies a single host. The subnet mask and wildcard mask are inverses of each other. The subnet mask (for example 255.255.255.0) has 1-bits for the network portion; the wildcard mask (0.0.0.255) has 1-bits for the host portion and is the form used in Cisco ACLs and OSPF configuration. The binary view colours the network bits and host bits differently so you can see the split directly.
FieldDescription
Network AddressThe first address in the block, with all host bits set to 0. Identifies the subnet and cannot be assigned to a host.
Broadcast AddressThe last address in the block, with all host bits set to 1. Traffic sent here reaches every host on the subnet.
Subnet MaskDotted-decimal mask (e.g. 255.255.255.0) whose 1-bits mark the network portion of the address.
Wildcard MaskThe bitwise inverse of the subnet mask (e.g. 0.0.0.255). Used in Cisco ACLs and OSPF area statements.
Total HostsThe full size of the block, 2 raised to the number of host bits. Includes the network and broadcast addresses.
Usable HostsAddresses assignable to devices — total minus 2 for most prefixes (with /31 and /32 as special cases).
IP RangeThe first and last usable addresses, i.e. the pool available for hosts, DHCP scopes, or static assignment.
IP ClassThe classful category (A–E) of the address based on its leading bits, retained for reference alongside CIDR.

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Common Subnet Calculator Use Cases

Plan VLANs and network segments

Divide an office or data-centre block into equal subnets sized to each department or VLAN. The subnet divider shows exactly how many hosts each segment gains so you can avoid over- or under-provisioning address space.

Write firewall and ACL rules

Confirm the exact network and broadcast addresses before writing allow/deny rules. The wildcard mask output drops straight into Cisco access lists and OSPF configuration without manual conversion.

Size DHCP scopes correctly

Read off the first and last usable addresses to define a DHCP pool that fits the subnet precisely, leaving room for gateways, printers, and other static assignments outside the dynamic range.

Study for networking certifications

CCNA, Network+, and similar exams test subnetting under time pressure. The colour-coded binary view and instant results make it easy to check your manual calculations and build an intuition for prefix lengths.

Subnet Calculator — Frequently Asked Questions

What is a subnet calculator?
A subnet calculator is a tool that takes an IP address and a CIDR prefix or subnet mask and computes all the derived values of that network: the network address, broadcast address, subnet mask, wildcard mask, total and usable host counts, and the range of assignable addresses. It removes the need to do binary AND/OR maths by hand and is used for network planning, firewall rules, DHCP scope design, and studying subnetting.
What does /24 mean in networking?
The /24 is CIDR notation meaning the first 24 bits of the 32-bit IPv4 address identify the network, leaving 8 bits for hosts. It is equivalent to the subnet mask 255.255.255.0. A /24 contains 256 total addresses (2^8), of which 254 are usable for hosts after subtracting the network and broadcast addresses. It is the most common prefix for small local networks.
How do I calculate usable hosts in a subnet?
Count the host bits — that is 32 minus the CIDR prefix. Raise 2 to that power to get the total number of addresses, then subtract 2 for the network and broadcast addresses. For example, a /26 has 6 host bits: 2^6 = 64 total addresses, minus 2 gives 62 usable hosts. The exceptions are /31 (2 usable, a point-to-point link) and /32 (a single host).
What is CIDR notation?
CIDR (Classless Inter-Domain Routing) notation writes a network as an address followed by a slash and a prefix length, such as 192.168.1.0/24. The prefix is the number of leading bits that identify the network. CIDR replaced the older class-based system (A, B, C) and allows networks of any size, which conserves address space and simplifies routing tables through route aggregation.
What is the difference between subnet mask and wildcard mask?
A subnet mask marks the network portion of an address with 1-bits, for example 255.255.255.0. A wildcard mask is its exact bitwise inverse, with 1-bits marking the host portion, for example 0.0.0.255. Subnet masks are used in interface configuration and general subnetting, while wildcard masks are used in Cisco access control lists and OSPF network statements. Both describe the same boundary from opposite directions.
What is a broadcast address?
The broadcast address is the last address in a subnet, formed by setting every host bit to 1. A packet sent to it is delivered to every host on that subnet. For 192.168.1.0/24 the broadcast address is 192.168.1.255. Because it is reserved for this purpose, it cannot be assigned to an individual device, which is one of the two addresses subtracted when counting usable hosts.
How to divide a network into smaller subnets?
To split a network you borrow bits from the host portion to create additional network bits. Borrowing 1 bit yields 2 subnets, 2 bits yields 4, 3 bits yields 8, and so on — n borrowed bits give 2^n subnets. For example, a /24 split into 4 subnets becomes four /26 networks of 62 usable hosts each. Enter the number of subnets you need in this tool and it borrows the right number of bits and lists every resulting subnet automatically.
What is /32 used for?
A /32 represents a single IP address — all 32 bits identify the host, so the block contains exactly one address. It is used for host routes, loopback interfaces, specifying a single address in firewall or ACL rules, and identifying an individual server in routing and load-balancer configuration. Because there is no host range, a /32 has one usable address and no separate network or broadcast address.
What is /30 subnet used for?
A /30 has 2 host bits, giving 4 total addresses and 2 usable hosts. It is the traditional choice for point-to-point links between two routers, where only two addresses are needed and the network and broadcast addresses are still reserved. Many networks now use /31 links instead (RFC 3021), which provide the same two usable hosts without wasting the extra two addresses.
How many hosts can a /24 subnet have?
A /24 subnet has 256 total addresses (2^8) and 254 usable hosts. The two addresses removed are the network address (192.168.1.0 in a typical example) and the broadcast address (192.168.1.255). The remaining 254 addresses, from .1 to .254, can be assigned to devices such as computers, printers, phones, and the default gateway.

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