IP Address Calculator: Subnet, CIDR & Network Planning Tool

April 19, 2026

🌐 IP Address Calculator

Calculate subnets, CIDR blocks, host ranges, wildcard masks & network addresses

⚡ Quick Presets
⚙️ Calculator Configuration
📋 Network Parameters
📐 VLSM Subnet Requirements
✅ Subnet Calculation Results
📊 Subnet Info Quick Reference
/24
Home Standard
254
Usable /24 Hosts
/30
P2P Links
16.7M
Max /8 Hosts
📋 CIDR Prefix Reference Table
CIDR Subnet Mask Total IPs Usable Hosts Block Size Common Use
/8255.0.0.016,777,21616,777,21416MLarge ISP / Class A
/12255.240.0.01,048,5761,048,5741MPrivate B (172.16)
/16255.255.0.065,53665,53464KCampus Network
/20255.255.240.04,0964,0944KLarge Office
/22255.255.252.01,0241,0221KMedium Office
/23255.255.254.0512510512Small Office
/24255.255.255.0256254256Home / SOHO
/25255.255.255.128128126128Guest WiFi
/26255.255.255.192646264IoT Segment
/27255.255.255.224323032Small VLAN
/28255.255.255.240161416Micro Segment
/29255.255.255.248868Server Cluster
/30255.255.255.252424Point-to-Point
/31255.255.255.25422*2P2P (RFC 3021)
/32255.255.255.255111Host Route

* /31 uses both addresses as per RFC 3021 for point-to-point links

🏷️ Private IP Address Ranges (RFC 1918)
Class Range CIDR Block Total IPs Typical Use
Class A Private10.0.0.0 – 10.255.255.25510.0.0.0/816,777,216Large enterprise, data center
Class B Private172.16.0.0 – 172.31.255.255172.16.0.0/121,048,576Medium enterprise
Class C Private192.168.0.0 – 192.168.255.255192.168.0.0/1665,536Home, SOHO, lab
Loopback127.0.0.0 – 127.255.255.255127.0.0.0/816,777,216Local host only
Link-Local169.254.0.0 – 169.254.255.255169.254.0.0/1665,536APIPA (no DHCP)
Multicast224.0.0.0 – 239.255.255.255224.0.0.0/4268,435,456Streaming, routing protocols
📈 Common Network Project Sizes
Project Hosts Needed Recommended CIDR Usable Hosts Spare Capacity
Single Home Lab10–25/27305–20 spare
Home Network25–50/24254200+ spare
Small Office50–100/2512626–76 spare
Medium Office100–250/242544–154 spare
Proxmox 3-Node15–30 VMs/27300–15 spare
IoT Segment20–50/266212–42 spare
Guest WiFi30–60/2512666–96 spare
Data Center Rack250–500/2351010–260 spare
💡 Tip: Always plan for growth. A /24 (254 hosts) feels large for a home lab of 10 devices today, but adding VMs, containers, and IoT devices can fill it faster than expected. Use the Growth Buffer dropdown to reserve capacity — 10–20% is standard practice per TIA-942 data center guidelines.
⚠️ VLSM Tip: Variable Length Subnet Masking (VLSM) lets you allocate exactly the right size subnet per department or function. Always sort your subnet requirements largest to smallest before allocating from your address space. This minimizes fragmentation and wasted IP addresses, especially critical in IPv4 networks with limited address space.

IP Address is a unique number that one gives to every device that connects to the net. It works like a rule that helps the devices talk to each other. Without that address the internet would not manage to identify the various computers, routers and pages.

Various devices, for instance phones, laptops, desktops and routers, all own IP Addresses.

What is an IP Address?

IP stands for Internet Protocol. It forms the basic layer for talking in networks that use pages, chat programs, live video and audio. One does not code an IP Address forever in the device.

It can change all along the time so one calls it a logical address instead of a lasting one.

In an IP Address hides two parts really. One of them is the network identifier, while the second is the host identifier. One calls subnet-mask that tool, that points to the routers, where the network section ends and the host starts.

The number after the slash, for instance /16, shows that 16 bits are used for the network part, and the rest for the hosts.

One gives a public IP Address to a device that directly will access the internet. That address is unique through the hole world of the net and it is assigned by the Internet Service Provider. On the other hand, a private IP Address works only for devices in the same local net.

It can look like 192.168.1.2. Imagine it as an internal letter in an office. You deliver something to the office itself, that is the router, and here one decides, to which desk it goes.

Two versions exist for IP handling. IPv4 uses numbers like 192.0.2.1, while IPv6 uses longer formats, for instance 2001:db8::42. Probably IPv6 slowly will replace IPv4, although that change moved very slowly.

IP Addresses do two main tasks: identify the network entry spot and give info about place. Thanks to them websites and programs can send data exactly to the right device. Your public IP comes from your ISP and can reveal basic local info, like country, city or the used provider.

Even so, an IP Address mainly shows the ISP, that manages a certain group of addresses, not a real person. It is possible to guess the general city or region from it, but not the exact home address.

In Windows, if you type “ipconfig” in the terminal, it shows the local IP. For Mac or Linux the command is “ifconfig“. If a device does not manage to receive a good address, it usually picks one that starts with 169.254; that is a link-local address.

Usually that means that somethingfailed with the network link.

Using a VPN, you can mask your IP Address and protect the online activity against outside parties. Some services offer a fixed IP, that stays the same and helps to skip CAPTCHAs or reach services on servers.

IP Address Calculator: Subnet, CIDR & Network Planning Tool

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