Subnet Calculator - FLSM, VLSM, Supernetting & IPv6 Calculator
Free online subnet calculator to instantly calculate IPv4 and IPv6 networks. Get network address, broadcast address, subnet mask, wildcard mask, CIDR notation, and usable IP address range in seconds. Supports IPv4 subnet calculator, CIDR calculator, FLSM (Fixed Length Subnet Mask), VLSM (Variable Length Subnet Mask), equal subnetting, and supernetting for route summarization.
Subnet Calculator
Subnet Input
Valid IPv4 required (e.g. 192.168.0.1)
Valid subnet mask required
FLSM Calculator — Fixed Length Subnet Masking
Fixed Length Subnet Masking (FLSM)
Valid IPv4 required (e.g. 192.168.0.1)
Valid subnet mask required
Must be a positive integer ≥ 1
Enter a valid host count
Fixed Length Subnetting
| Subnet Name | Network | First Usable IP | Last Usable IP | Broadcast | Total Usable Host | Total Available Host | Netmask | Wildcard |
|---|
Free/Unused IP Network
| Subnet Name | Network | First Usable IP | Last Usable IP | Broadcast | Total Usable Host | Total Available Host | Netmask | Wildcard |
|---|
Equal Host Calculator
Equal Host Subnetting
Valid IPv4 required (e.g. 192.168.0.1)
Valid subnet mask required
Enter a valid host count
Equal Host Subnetting
| Subnet Name | Network | First Usable IP | Last Usable IP | Broadcast | Total Usable Host | Total Available Host | Netmask | Wildcard |
|---|
VLSM Calculator — Variable Length Subnet Masking
Variable Length Subnet Masking (VLSM)
Valid IPv4 required (e.g. 192.168.0.1)
Valid subnet mask required
Enter comma-separated positive integers
Variable Length Subnetting
| Subnet Name | Network | First Usable IP | Last Usable IP | Broadcast | Total Usable Host | Total Available Host | Netmask | Wildcard |
|---|
Free/Unused IP Network
| Subnet Name | Network | First Usable IP | Last Usable IP | Broadcast | Total Usable Host | Total Available Host | Netmask | Wildcard |
|---|
Supernetting Calculator — Route Summarization
Supernetting (IP Route Summarization)
Example Input:
192.168.1.0/24
192.168.2.0/24
192.168.3.0/24
192.168.4.0/24
192.168.2.0/24
192.168.3.0/24
192.168.4.0/24
Enter ≥ 2 valid networks in CIDR notation
Route Summarization Results
🎯 Summary Network Details
| Summary Network | First Usable IP | Last Usable IP | Broadcast | Total Usable Host | Total Available Host | Netmask | Wildcard |
|---|
📋 Individual Networks
| Network | First Usable IP | Last Usable IP | Broadcast | Total Usable Host | Total Available Host | Netmask | Wildcard |
|---|
IPv6 Calculator
IPv6 Subnet
Valid IPv6 required (e.g. 2001:db8::1)
How to Use the calculator
Free online subnet calculator to instantly calculate IPv4 and IPv6 networks. Get network address, broadcast address, subnet mask, wildcard mask, CIDR notation, and usable IP address range in seconds. Supports IPv4 subnet calculator, CIDR calculator, FLSM (Fixed Length Subnet Mask), VLSM (Variable Length Subnet Mask), equal subnetting, and supernetting for route summarization.
1. Subnet Calculator
192.168.1.10)./24).Example Results (192.168.1.10 / 24)
| Network Address | 192.168.1.0/24 |
|---|---|
| First Usable IP | 192.168.1.1 |
| Last Usable IP | 192.168.1.254 |
| Broadcast Address | 192.168.1.255 |
| Total Usable Hosts | 254 |
| Subnet Mask | 255.255.255.0 |
2. FLSM Calculator (Fixed Length)
Example Results (IP: 192.168.1.0/24 | Subnets: 2 | Hosts: 100)
| Subnet Name | Network | First Usable IP | Last Usable IP | Broadcast | Total Usable Host | Total Available Host | Netmask | Wildcard |
|---|---|---|---|---|---|---|---|---|
| Subnet 1 | 192.168.1.0/25 | 192.168.1.1 | 192.168.1.126 | 192.168.1.127 | 126 | 128 | 255.255.255.128 | 0.0.0.127 |
| Subnet 2 | 192.168.1.128/25 | 192.168.1.129 | 192.168.1.254 | 192.168.1.255 | 126 | 128 | 255.255.255.128 | 0.0.0.127 |
3. Equal Host Calculator
Example Results (IP: 10.0.0.0/24 | Hosts per Subnet: 60)
| Subnet Name | Network | First Usable IP | Last Usable IP | Broadcast | Total Usable Host | Total Available Host | Netmask | Wildcard |
|---|---|---|---|---|---|---|---|---|
| Subnet 1 | 10.0.0.0/26 | 10.0.0.1 | 10.0.0.62 | 10.0.0.63 | 62 | 64 | 255.255.255.192 | 0.0.0.63 |
| Subnet 2 | 10.0.0.64/26 | 10.0.0.65 | 10.0.0.126 | 10.0.0.127 | 62 | 64 | 255.255.255.192 | 0.0.0.63 |
| Subnet 3 | 10.0.0.128/26 | 10.0.0.129 | 10.0.0.190 | 10.0.0.191 | 62 | 64 | 255.255.255.192 | 0.0.0.63 |
| Subnet 4 | 10.0.0.192/26 | 10.0.0.193 | 10.0.0.254 | 10.0.0.255 | 62 | 64 | 255.255.255.192 | 0.0.0.63 |
4. VLSM Calculator (Variable Length)
100, 50, 20).Example Results (IP: 192.168.1.0/24 | Hosts: 100, 50, 20)
| Subnet Name | Network | First Usable IP | Last Usable IP | Broadcast | Total Usable Host | Total Available Host | Netmask | Wildcard |
|---|---|---|---|---|---|---|---|---|
| Subnet 1 | 192.168.1.0/25 | 192.168.1.1 | 192.168.1.126 | 192.168.1.127 | 126 | 128 | 255.255.255.128 | 0.0.0.127 |
| Subnet 2 | 192.168.1.128/26 | 192.168.1.129 | 192.168.1.190 | 192.168.1.191 | 62 | 64 | 255.255.255.192 | 0.0.0.63 |
| Subnet 3 | 192.168.1.192/27 | 192.168.1.193 | 192.168.1.222 | 192.168.1.223 | 30 | 32 | 255.255.255.224 | 0.0.0.31 |
5. Supernetting Calculator
Example Results (Inputs: 172.16.0.0/24 and 172.16.1.0/24)
| Summary Network | First Usable IP | Last Usable IP | Broadcast | Total Usable Host | Total Available Host | Netmask | Wildcard |
|---|---|---|---|---|---|---|---|
| 172.16.0.0/23 | 172.16.0.1 | 172.16.1.254 | 172.16.1.255 | 510 | 512 | 255.255.254.0 | 0.0.0.255 |
6. IPv6 Calculator
Example Results (IP: 2001:db8:acad::1 | Prefix: /64)
| Network Address | 2001:db8:acad::/64 |
|---|---|
| Full IPv6 Address | 2001:0db8:acad:0000:0000:0000:0000:0001 |
| Compressed Address | 2001:db8:acad::1 |
| First Address | 2001:db8:acad:: |
| Last Address | 2001:db8:acad:0:ffff:ffff:ffff:ffff |
Frequently Asked Questions — Subnet Calculator
What is a Subnet Calculator and what does it calculate?
A Subnet Calculator computes the key details of an IP network segment from a given IP address and subnet mask or CIDR prefix. It outputs the network address, broadcast address, first and last usable host IPs, subnet mask, wildcard mask, total usable hosts, and total available host addresses.
What is CIDR notation and how does it relate to subnet masks?
CIDR (Classless Inter-Domain Routing) notation expresses a network as IP/prefix (e.g., 192.168.1.0/24). The slash number is the prefix length — the count of network bits. /24 equals subnet mask 255.255.255.0, /16 equals 255.255.0.0, and /8 equals 255.0.0.0. Our calculator converts automatically between both formats.
What is the difference between FLSM and VLSM?
FLSM (Fixed Length Subnet Masking) divides a network into equal-sized subnets — every subnet has the same prefix and the same host capacity. VLSM (Variable Length Subnet Masking) assigns each subnet a different prefix size based on its individual host requirement, minimising IP address waste. VLSM is used in modern networks; FLSM is simpler and used for uniform segmentation.
How many usable hosts are in a /24, /25, /26, /27, /28, /29, /30 subnet?
/24 = 254 hosts (256−2), /25 = 126, /26 = 62, /27 = 30, /28 = 14, /29 = 6, /30 = 2. The formula is 2^(32−prefix)−2. A /31 has 2 addresses usable for point-to-point (RFC 3021) and a /32 is a single host route with 1 address. Enter any prefix in our Subnet Calculator to get the exact count instantly.
What is a wildcard mask and how is it different from a subnet mask?
A wildcard mask is the bitwise inverse of a subnet mask. Where a subnet mask has a 1, the wildcard has a 0, and vice versa. For /24 (255.255.255.0) the wildcard is 0.0.0.255. Wildcard masks are used in Cisco ACLs and OSPF to specify which IP bits must match.
What is Supernetting (Route Summarization)?
Supernetting merges multiple contiguous subnets into a single larger network with a shorter prefix. For example, four /24 networks (192.168.0.0–192.168.3.0) summarise as 192.168.0.0/22. This reduces the number of routing table entries, improving routing efficiency and reducing overhead on routers and routing protocols.
How does the VLSM Calculator work?
Enter a base IP, subnet mask, and comma-separated host requirements (e.g., 100,50,20,10). The VLSM Calculator sorts them largest-first, then for each requirement calculates the smallest prefix that fits the host count using the formula: prefix = 32 − ceil(log₂(hosts+2)). It allocates subnets sequentially from the base address and shows any unused IP blocks as free subnets.
What IPv6 prefix lengths does the IPv6 Calculator support?
The IPv6 Calculator supports all prefix lengths from /0 to /128. Common assignments include /48 for site allocations, /64 for individual subnets (the standard LAN size), and /128 for host routes. The calculator shows total addresses (as a large integer), network prefix, interface ID, address type, and scope for any prefix.
What is the broadcast address and why can't I assign it to a host?
The broadcast address is the last IP in a subnet (all host bits set to 1). Packets sent to this address are delivered to every device in the subnet simultaneously. Because it is reserved for broadcast communication, it cannot be assigned as a host IP. In 192.168.1.0/24, the broadcast address is 192.168.1.255.
What are private IP address ranges?
Private ranges defined by RFC 1918 are: 10.0.0.0/8 (Class A, ~16.7 million IPs), 172.16.0.0/12 (Class B, ~1 million IPs), and 192.168.0.0/16 (Class C, 65,536 IPs). These are not routable on the public internet and are used for internal LAN, data centre, and VPN addressing. Our Subnet Calculator shows the IP class in the Subnet Details results.
Can I calculate subnets for public IP ranges?
Yes. All subnet tools on this page work with any valid IPv4 address — private (RFC 1918), public, loopback (127.x.x.x), link-local (169.254.x.x), or multicast ranges. The IP Type field in Subnet Details tells you whether the address is Private or Public.
What is a /31 subnet used for?
A /31 subnet (RFC 3021) contains exactly 2 IP addresses, both usable for point-to-point router interconnects. There is no network address or broadcast address in a /31 — both IPs are assignable. This makes /31s more efficient than /30s for WAN links where you only need two addresses.
What is a /32 subnet?
A /32 subnet is a host route representing a single specific IP address. It has no network or broadcast address. /32s are used in routing tables to advertise loopback IPs, virtual IPs (VIPs) on load balancers, or to apply very specific ACL rules. They appear commonly in BGP and OSPF configurations.
How do I find the supernet (summary route) for multiple subnets?
Click the Supernetting Calculator tab. Enter two or more contiguous networks in CIDR notation, one per line. The calculator aligns the network bits of all inputs, finds the shortest prefix that covers them all, and returns the summary network with full details. Networks that are not contiguous or not power-of-2 aligned will return an error.
What does the Equal Host Calculator do differently from FLSM?
The FLSM Calculator asks for both the number of subnets and the hosts per subnet, then verifies they fit. The Equal Host Calculator takes only a host count and automatically calculates how many equal subnets of that size can fit in your base network. It is a faster workflow when you want to know "how many subnets of X hosts can I make from this network?"
Is my calculation data sent to a server?
No. All subnet calculations are performed entirely in your browser using JavaScript. No IP address data, network ranges, or any other inputs are transmitted to any server. The tool works fully offline once the page is loaded.
Can I download the subnet calculation results?
Yes. Every results panel includes a Download button that exports the subnet table as a CSV file — ready to open in Microsoft Excel, Google Sheets, or any spreadsheet application. The Copy button copies the data as tab-separated values, perfect for pasting directly into a spreadsheet or document.
What is the difference between Total Usable Hosts and Total Available Hosts?
Total Available Hosts is the total number of IP addresses in the subnet (2^host_bits), including the network address and broadcast address. Total Usable Hosts subtracts those two reserved addresses (2^host_bits − 2) and represents how many IPs can actually be assigned to devices. For a /24: Available = 256, Usable = 254.
What IPv6 address types does the IPv6 Calculator identify?
The IPv6 Calculator identifies: Unicast, Multicast (FF::/8), Loopback (::1), Unspecified (::), Link-Local (FE80::/10), Unique Local (FC00::/7), Documentation (2001:DB8::/32), 6to4 (2002::/16), and Teredo (2001::/32). It also shows the scope: Global, Link-Local, Site-Local, or Host.
Why do my supernet networks fail with "not contiguous" error?
For supernetting to work, the input networks must be strictly contiguous — they must be sequential with no gaps, and the combined block must align to a power of 2 on the correct boundary. For example, 192.168.1.0/24 and 192.168.3.0/24 fail because 192.168.2.0/24 is missing. Ensure there are no gaps between your input networks.