Subnet calculatorCalculators

Subnet calculator. CIDR in, every range out.

Type an address such as 192.168.1.130/26 or 10.0.0.5 255.255.252.0. You get the network and broadcast addresses, the first and last usable host, the masks, the host count and a split into smaller subnets. IPv4 only.

Cost to you

Free

Runs in your browser. No signup, no API call, no limit per hour.

browser
runs in: none
API calls: none
account

Use it now

Use the Subnet calculator here

It runs in your browser. Nothing you type is sent anywhere, there is no signup and no limit.

Address

IPv4 address with a prefix or a mask

Examples

Subnet

Network: 192.168.1.128/26
Network address: 192.168.1.128
Broadcast address: 192.168.1.191
First usable host: 192.168.1.129
Last usable host: 192.168.1.190
Usable hosts: 62
Total addresses: 64
Subnet mask: 255.255.255.192
Wildcard mask: 0.0.0.63
Prefix length: /26
IP class: C
Address type: Private (RFC 1918)

Address 11000000.10101000.00000001.10000010

Mask 11111111.11111111.11111111.11000000

Split into smaller subnets

New prefix length

Subnet	First host	Last host	Broadcast
192.168.1.128/28	192.168.1.129	192.168.1.142	192.168.1.143
192.168.1.144/28	192.168.1.145	192.168.1.158	192.168.1.159
192.168.1.160/28	192.168.1.161	192.168.1.174	192.168.1.175
192.168.1.176/28	192.168.1.177	192.168.1.190	192.168.1.191

Calculated in your browser. IPv4 only. /31 and /32 follow RFC 3021, where every address is usable.

Run it from your agent

Copy one prompt, give it to your agent.

Fill in the placeholder, paste it, and the agent runs the same job with current data on your looot account and shows the cost.

You give it: an ipv4 address with a cidr prefix or a subnet mask.
Billed per call, nothing while your agent is idle.
The agent shows the price before it calls.

Prompt: Subnet calculator

Use looot to check who owns the addresses in a network block. 1. Set up https://looot.ai/skill.md. 2. Work out the first and last usable host of [CIDR, for example 203.0.113.0/28]. 3. Search the catalog for an IP lookup endpoint and check its price before you call. 4. Look up the first and last host. 5. Return the owner, country and network type for each.

Give this to your agent

Setup command

set up looot - https://looot.ai/skill.md

What comes back

What your agent gets from subnet calculator

Field names as the providers return them. The exact set varies by endpoint, and your agent reads it from the catalog.

network and broadcast address
first and last usable host
subnet and wildcard mask
usable host count
list of smaller subnets

Use it for

What people do with subnet calculator

Plan a VPC
Split a /16 into /24 subnets for each zone and copy the list as CSV.
Write firewall rules
Get the wildcard mask for an ACL or check the range a rule covers.
Read a CIDR
See at once how many hosts a /27 holds and where it starts and ends.
Study for exams
Check subnetting answers with the address and mask in binary.

Set up once

Three steps. Your agent does the rest.

Paste one prompt into your agent

Set up looot

Done, looot is connected.

Copy one prompt from /connect into Claude Code, Cursor, or any MCP agent. No SDK, no dashboard click-through first.

Your agent finds the right operation

Hunter$0.0265

Exa$0.0090

Diffbot$0.0032

The agent finds the operation it needs and sees the price first. It calls nothing blind.

You watch what it cost

Hunter$0.0265

Exa$0.0090

Diffbot$0.0032

Total$0.0387

Every call settles for its quoted price and lands in the ledger. You always know what ran and what it cost.

Keep going

Lookups
IP lookup
Country, continent, ASN and network owner for any public IPv4 or IPv6 address.
Runs a real API callprice on request
Converters
Binary to text converter
Converts binary, hex, decimal or octal bytes to UTF-8 text and back, with format detection and a per character table.
Free, no signupno limit
Converters
Unix timestamp converter
Unix timestamps to dates in any time zone and back, with the unit detected from the number of digits.
Free, no signupno limit

FAQ

Questions about subnet calculator

Apply the mask to the address with a bitwise AND to get the network address. Set all host bits to 1 for the broadcast address. The hosts are everything in between. Type the address and prefix here and every value appears.

254. A /24 has 256 addresses, and the network and broadcast addresses are not assigned to hosts. In general a prefix of n gives 2 to the power of (32 minus n) addresses, minus 2.

A /31 has two addresses and RFC 3021 lets both be used on a point to point link. A /32 is one host. The page counts every address in these as usable.

Yes. Type the address, a space and the mask, such as 10.0.0.5 255.255.252.0. A mask with gaps in its 1 bits is rejected because it is not a valid subnet mask.

The inverse of the subnet mask: 0.0.0.255 for a /24. Cisco ACLs and OSPF use it to say which bits may vary.

Pick a longer prefix under Split. A /22 split into /24 gives four subnets. The table lists up to 256 rows, and the CSV holds the same rows.

No, IPv4 only for now. An IPv6 address is rejected with an error.

Yes. Address type shows private (RFC 1918), carrier-grade NAT, loopback, link-local, multicast or public.

For agents

tool: Subnet calculator
category: Calculators
input: An IPv4 address with a CIDR prefix or a subnet mask
output: network and broadcast address, first and last usable host, subnet and wildcard mask, usable host count, list of smaller subnets
price: per call, read live from the catalog on the web page
web tool: runs in the visitor's browser, no API call, free and unlimited
schedule: on demand
setup: https://looot.ai/skill.md
llms.txt: https://looot.ai/llms.txt
updated: 2026-10-14

markdown /free-tools/subnet-calculator.md

Run subnet calculator from your own agent.

Start your workspace, top up, and paste the prompt into the agent you already use. It runs the job with live data and shows the cost first.

Start your workspace See all free tools