All-in-One IPv4 Subnet Calculator

Get an instant breakdown of any IPv4 network before running deeper calculations. If you only need standard network boundaries, try our dedicated Subnet Calculator.

1. 1Enter your IP Address (e.g., 192.168.1.0).
2. 2Type a Subnet Mask (e.g., 255.255.255.0) or simply drag the live CIDR Slider.
3. 3The Subnet Details panel updates in real-time to show the network address, usable host range, broadcast address, and wildcard mask.

Example output for 192.168.1.0 / 255.255.255.0:

FLSM divides a network block into equal-sized subnets. This is ideal when all network segments require the exact same number of IP addresses. For a streamlined interface, use our standalone FLSM Calculator.

1. 1Enter your base IP (e.g., 192.168.0.0) and subnet mask / CIDR to define the total IP pool.
2. 2Select the FLSM mode checkbox.
3. 3Set the No. of Subnets — how many equal subnets you need (e.g., 3).
4. 4Set Hosts per Subnet (e.g., 50). The tool will calculate the most efficient power-of-2 block size.
5. 5Click Calculate. Any leftover address space will be listed in the Free/Unused IP panel.

Example: 192.168.0.0/24 · No. of Subnets 3 · Hosts 50

Equal Hosts mode works like FLSM but removes one step — you enter only the host count and the calculator automatically fills in the maximum number of equal subnets that fit. No Free/Unused IP table is generated because the base network is fully consumed. Prefer a dedicated view? Try our Equal Host Subnet Calculator.

1. 1Enter your base IP Address and set the CIDR slider to define the total address pool.
2. 2Tick the Equal Hosts checkbox. The No. of Subnets field becomes read-only and the Hosts per Subnet field switches to single-number mode.
3. 3Type the number of hosts each subnet needs (e.g. 50). The No. of Subnets field updates automatically to show the maximum number of equal subnets that fit.
4. 4Click Calculate. All equal subnets are listed — no free IP table is shown because every address is allocated.

Example: 192.168.0.0/24 · Hosts per Subnet 50 · No. of Subnets auto-fills to 4

VLSM is the most efficient way to allocate IP addresses, allowing you to create subnets of varying sizes based on exact host requirements to minimize IP waste. Prefer a dedicated view? Try our VLSM Calculator.

1. 1Enter your base IP (e.g., 192.168.0.0) and set the CIDR slider to define the total address pool.
2. 2Tick the VLSM checkbox. The Hosts per Subnet field will switch to comma-separated mode and the No. of Subnets field becomes read-only — it will auto-fill based on how many host values you enter.
3. 3In the Hosts per Subnet field, enter the number of hosts required for each subnet, separated by commas (e.g., 100,50,20,10). You can enter them in any order — the calculator automatically sorts largest-to-smallest for optimal allocation. As you type, No. of Subnets updates live to reflect the count.
4. 4Click Calculate. Each subnet gets the tightest possible prefix, and any remaining address space is shown in the Free/Unused IP Network table as correctly boundary-aligned CIDR blocks.

Example: 192.168.0.0/24 · Hosts 100,50,20,10 · No. of Subnets auto-fills to 4

Supernetting combines multiple contiguous networks into a single, optimized summary route, drastically reducing routing table size and improving network convergence. We also offer a dedicated Supernetting Calculator.

1. 1Locate the Supernetting text box in the calculator.
2. 2Enter two or more CIDR networks, placing one per line (e.g., 192.168.0.0/24 on line one, 192.168.1.0/24 on line two).
3. 3Ensure your networks are contiguous (no gaps) and form a valid power-of-2 block.
4. 4Click Calculate to output the single, perfectly aligned summary route.

Example: summarizing 4 × /24 networks → one /22

A subnet calculator takes an IP address and a subnet mask (or CIDR prefix) and returns the complete network breakdown: network address, first and last usable host, broadcast address, total hosts, wildcard mask, and binary mask. This calculator also shows IP class and whether the address is private or public.

They represent the same thing in different formats. A subnet mask like 255.255.255.0 uses four dotted-decimal octets; a CIDR prefix like /24 counts how many leading bits are set to 1. You can use either format in this calculator — they are interchangeable.

Fixed-Length Subnet Masking (FLSM) divides a network into subnets of the exact same size — every subnet uses the same mask and supports the same number of hosts. Variable-Length Subnet Masking (VLSM) allocates subnets of varying sizes based on actual host requirements. VLSM wastes far fewer addresses in real deployments.

Use FLSM when all your network segments genuinely need the same number of hosts — for example, a structured lab environment or a legacy network that requires identical subnet sizes for administrative simplicity. In most modern production networks, VLSM is preferred because it uses address space more efficiently.

VLSM sorts your host requirements from largest to smallest and allocates the smallest subnet that fits each requirement in turn. For example, if you need 100, 50, and 20 hosts from a /24, it assigns a /25 (126 usable), then a /26 (62 usable), then a /27 (30 usable) — using the minimum prefix that satisfies each count. This leaves the maximum free space for future subnets.

Yes. After every FLSM or VLSM calculation the calculator generates a Free/Unused IP Network table showing exactly which address blocks remain unallocated. This is useful when planning future subnet expansion or auditing existing address space.

Supernetting combines multiple contiguous smaller networks into a single, larger summary route. This reduces routing table size in core routers, lowers memory usage, and improves convergence time. Use our dedicated Supernetting Calculator for more detail.

Three rules must be satisfied: (1) the networks must be contiguous with no gaps between them, (2) the number of networks being summarized must be a power of 2 (2, 4, 8, 16…), and (3) the first network must fall on the correct boundary for the summary prefix. If any rule is broken, the calculator will warn you and still show the closest valid summary, but that summary may cover unintended addresses.

No. Every tool on this site is completely free and runs entirely in your browser — no login, no installation, and no usage limits. All calculations happen locally; your IP addresses are never sent to a server.

This page focuses on IPv4. For IPv6 use our dedicated IPv6 Subnet Calculator, which handles any prefix from /0 to /128 and shows address type, scope, EUI-64 details, and more.

We have 19 free tools covering subnet calculation, VLSM, FLSM, supernetting, subnet overlap checking, IPv6 calculation, SLAAC/EUI-64 generation, IPv6 compression, IP range to CIDR conversion, wildcard mask conversion, reverse IP, MAC address conversion, IP cleaning, and more. See the About page or the Quick Links section below for the full list.

Yes. All calculations use the same bitwise logic a router uses internally. Results are correct for production network planning, CCNA and CCNP exam preparation, firewall rule writing, and cloud VPC design. If you ever find a discrepancy, please contact us and we will investigate immediately.