Zerdly

IP Range Calculator

An exact IPv4 and IPv6 subnet workbench: network, mask, usable range and counts, address ranges to CIDR blocks, contains, split and aggregate.

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How to use this calculator

Enter

How to read a /31

Result

192.168.1.0/24

Conventional subnet: the first address names the network and the last is the directed broadcast.

You entered 192.168.1.10, which has host bits set; the network it belongs to is shown.

Network
192.168.1.0/24
Subnet mask
255.255.255.0
Wildcard mask
0.0.0.255
Total addresses
256
Usable addresses
254
First usable
192.168.1.1
Last usable
192.168.1.254
Broadcast
192.168.1.255
First address
192.168.1.0
Last address
192.168.1.255
Registered purpose
Private-Use (RFC 1918)
24 network bits (shaded) · 8 host bits

Calculated in your browser. No address is looked up, pinged or scanned. Purpose labels: IANA special-purpose registries, 2025-10-09 (checked 2026-10-08).

How to use this calculator

  1. Choose IPv4 or IPv6 and a calculation: address + prefix, address + mask, range to CIDR blocks, contains, split or aggregate.
  2. Type or paste an address — 192.168.1.10/24 works as it is. Host bits are allowed and the tool says when it removed them.
  3. Read the network, mask, usable range and exact counts, and copy the CIDR, the mask or the whole summary.

How it works

An IPv4 address is a 32-bit number and the prefix says how many leading bits are the network. A block of prefix p holds 2^(32−p) addresses; the network is the address with every host bit cleared and the last address has them all set. Counts are exact integers at every prefix, so a /0 is 4,294,967,296 addresses.

Range to CIDR takes, at each step, the largest power-of-two block that starts exactly at the current address and does not pass the end, so the list is the shortest one that covers exactly your range. Aggregate merges blocks into the fewest that cover exactly the same addresses — it never adds any.

IPv6 works the same way with 128 bits, written in the RFC 5952 short form. IPv6 has no broadcast, so nothing is subtracted.

Worked example

192.168.1.10/24, and the range .1 to .6. 192.168.1.10/24 is network 192.168.1.0/24: 256 addresses, 254 usable (.1 to .254), mask 255.255.255.0, wildcard 0.0.0.255. The range 192.168.1.1–192.168.1.6 needs four blocks: .1/32, .2/31, .4/31 and .6/32.

Frequently asked questions

Why are there two fewer usable hosts?

In a conventional IPv4 subnet the first address names the network and the last is the directed broadcast, so a /24 gives 256 − 2 = 254 usable hosts.

How many usable addresses does a /31 have?

Two, on a point-to-point link: RFC 3021 lets both addresses of a /31 be used and drops the broadcast, which is how most routers treat it. Read as a conventional subnet it would have none. The calculator lets you choose and says which reading it applied.

And a /32?

A /32 is a single address — a host route. That one address is the host, so the count is 1; there is no broadcast to exclude.

Does the tool look up or scan my address?

No. Everything is arithmetic on what you type, in your browser. The purpose label (private, documentation, loopback and so on) comes from a copy of the IANA special-purpose registries, matched by longest prefix rather than guessed from the first number.

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Cite this tool

Zerdly. (2026). IP Range Calculator. Retrieved from https://www.zerdly.com/tools/ip-range-calculator/

Tip: Enter any known values to calculate the remaining results.

Designed to run locally in your browser. Tool inputs are not intentionally stored by Zerdly unless stated otherwise.