Ip Range Calculator

IP Address:

CIDR Prefix Length:

Every device on an IP network — your laptop, phone, printer, or server — needs an address, and those addresses are organized into blocks called subnets. The single most important question when working with any subnet is: which addresses belong to my network, and which ones can I actually assign to devices? Answering it by hand means converting dotted-decimal addresses into 32-bit binary numbers, performing bitwise AND operations, and carefully counting hosts. It is slow, tedious, and a single slipped bit ruins the whole answer.

Our free IP Range Calculator eliminates that pain completely. Enter any IPv4 address and a CIDR prefix length (the number after the slash, like the “24” in 192.168.1.0/24), and the tool instantly computes the subnet mask, the network address, the broadcast address, the full range of usable IP addresses, and exactly how many hosts you can connect. Network administrators use it to plan and document subnets, IT students use it to check their certification homework, and home-lab enthusiasts use it to carve up their home networks for servers, smart-home gadgets, and guest Wi-Fi. Everything runs right in your browser — no sign-up, no software to install, and results appear the moment you click Calculate.

How to Use the IP Range Calculator

Getting your results takes less than a minute:

Enter the IP address. Type any valid IPv4 address, for example 192.168.1.10. It can be any address inside the subnet you want to analyze — it does not need to be the network address itself.
Enter the CIDR prefix length. This is a number from 0 to 32. Enter 24 for a typical home or small-office network (the equivalent of subnet mask 255.255.255.0), 16 for a larger network, or 30 for a point-to-point link.
Click the Calculate button. The subnet mask, network address, broadcast address, usable IP range, and usable host count appear immediately below.
Click Reset (on the right of the Calculate button) to clear everything and start a fresh calculation.

Worked Example

Imagine your office router sits at 192.168.1.10 and the office network is a /24. You need to assign a static address to a new network printer and want to know which addresses are safe to use.

Type 192.168.1.10 into the IP Address field.
Type 24 into the CIDR Prefix Length field.
Click Calculate.

The calculator returns:

Subnet Mask: 255.255.255.0
Network Address: 192.168.1.0 — identifies the network itself; never assign it to a device.
Broadcast Address: 192.168.1.255 — reaches every device at once; also never assignable.
Usable IP Range: 192.168.1.1 – 192.168.1.254 — the addresses you can hand out.
Usable Hosts: 254

You now know the printer can safely take any free address between 192.168.1.1 and 192.168.1.254 — just avoid ones already in use, like the router’s own .10 or addresses in the DHCP pool.

More Helpful Information

Understanding CIDR notation

CIDR (Classless Inter-Domain Routing) notation writes a network as an address plus a prefix length, for example 10.0.0.0/8. The prefix length is simply the count of leading “network bits” — the bits that identify the network rather than individual hosts. A longer prefix means a smaller network: /24 gives 254 usable hosts, /16 gives 65,534, and /8 gives over 16 million. The remaining bits are the “host bits,” and the total number of addresses in the block is always 2 raised to the power of the host-bit count.

Common prefix sizes cheat sheet

/32 — a single host address, used in routing tables and firewall rules.
/31 — point-to-point links with 2 usable addresses (no broadcast address is reserved, per RFC 3021).
/30 — point-to-point links with 2 usable hosts; the classic choice for router-to-router connections.
/29 — 6 usable hosts; handy for a tiny branch office.
/24 — 254 usable hosts; the standard small-to-medium LAN.
/16 — 65,534 usable hosts; a large organization network.
/8 — 16,777,214 usable hosts; huge enterprise or ISP-level blocks.

Private versus public address ranges

Three blocks are reserved for private internal use and are never routed on the public internet: 10.0.0.0/8, 172.16.0.0/12, and 192.168.0.0/16. If the address you enter falls inside one of these ranges, you are working with an internal network — the normal case for offices, labs, and homes. Anything else is (in principle) a publicly routable address.

Mistakes to avoid

The classic error is assigning the network address or the broadcast address to a device, which breaks connectivity for that machine. Another common mistake is forgetting that routers, DHCP servers, and existing static devices already occupy part of the range — always check what is taken before assigning something new. Finally, remember that the usable host count shown by the calculator already excludes the network and broadcast addresses, so you never need to subtract them yourself.

Frequently Asked Questions

1. What is an IP range?
An IP range is the complete block of IP addresses defined by a network address and its subnet mask. It includes the network address, the broadcast address, and every usable host address in between.

2. What is CIDR notation?
CIDR notation is a compact way to describe a network, written as an IP address followed by a slash and a prefix length, for example 192.168.1.0/24. The prefix length tells you how many leading bits identify the network.

3. What is the difference between a subnet mask and a CIDR prefix?
They express the same information in different forms. A CIDR prefix like /24 counts the network bits, while the equivalent subnet mask 255.255.255.0 shows those bits as a dotted-decimal address. The calculator converts between them automatically.

4. Why can’t I use the network address for a device?
The network address identifies the subnet itself and is used by routers to make forwarding decisions. Assigning it to a device creates an address conflict in the routing logic and the device will not communicate properly.

5. Why can’t I use the broadcast address for a device?
The broadcast address is reserved for sending traffic to every host on the network simultaneously. Giving it to a single device breaks that mechanism and causes connectivity failures.

6. How many usable hosts does a /24 network have?
A /24 network has 256 total addresses minus the network and broadcast addresses, leaving 254 usable hosts.

7. What is the usable range of 10.0.0.0/8?
The network address is 10.0.0.0, the broadcast address is 10.255.255.255, and the usable range is 10.0.0.1 through 10.255.255.254, giving 16,777,214 usable hosts.

8. Can I enter any IP address, or must it be the network address?
You can enter any address inside the subnet. The calculator derives the network address from your input, so 192.168.1.10/24 and 192.168.1.0/24 produce identical results.

9. What are private IP address ranges?
The private ranges are 10.0.0.0/8, 172.16.0.0/12, and 192.168.0.0/16. They are reserved for internal networks and are not routed across the public internet.

10. What is a /31 subnet used for?
A /31 subnet is used for point-to-point links between two routers. It contains exactly 2 addresses and, under RFC 3021, neither is wasted on network or broadcast, so both are usable.

11. How do I choose the right subnet size?
Count the devices you need to address, add room for growth (at least 20–30 percent), then pick the smallest prefix that fits. For 40 devices, a /26 (62 usable hosts) is a good fit; for 300 devices, use a /23 (510 usable hosts).

12. Does this calculator support IPv6?
No. This tool works with IPv4 addresses only (the familiar four-number format like 192.168.1.1). IPv6 uses a completely different 128-bit addressing scheme.

13. Why does my usable host count differ from 2^n?
The raw block size is 2 raised to the number of host bits, but the network and broadcast addresses are reserved, so the usable count is always 2 fewer — except for /31 and /32, which follow special rules.

14. What should I do before assigning a static IP?
Verify the address is inside your usable range, confirm it is not already taken by another device or inside the DHCP pool, and document the assignment so future changes don’t create conflicts.

15. Is the IP Range Calculator free to use?
Yes. It is completely free, works instantly in your browser, and you can run as many calculations as you need without creating an account.