IP Range Calculator Online: Turn a CIDR Address Into the Full Usable Range
CodexFuse Team · 2026-10-31T15:15:47.988Z · 9 min read min read
Free IP range calculator: turn any IPv4 address and CIDR prefix into the network, broadcast, mask and usable address range, with a worked office example.
An ip range calculator answers a question every network change starts with: if I use this address block, which addresses can I actually assign, and which ones must I leave alone? You type in an IPv4 address and a CIDR prefix, and you get the network address, the broadcast address, the subnet mask, and the first and last usable addresses in one pass.
That matters because one wrong boundary can take an office offline: a broadcast address given to a printer never connects, and two overlapping ranges make devices fight over the same address.
This guide shows how the free CodexFuse IP Range Calculator works, walks through one complete office example with real numbers, and explains where the tool stops so you do not mistake a calculation for a network design.
What does an IP range calculator do?
An ip range calculator takes an IPv4 address and a CIDR prefix, such as 192.168.10.0/26, and works out the full address block that prefix defines. It returns the network address, the broadcast address, the subnet mask in dotted form, the total number of addresses, the usable range, and how many hosts you can actually assign.
Think of the CIDR prefix as the size of the box: a /24 holds 256 addresses, a /26 holds 64, and a /25 holds 128. The smaller the number after the slash, the bigger the box.
The CodexFuse tool keeps the input small: an IPv4 address and a CIDR prefix, with no spreadsheet formula or binary conversion to do by hand.
Why do IP ranges go wrong in small offices?
IP ranges go wrong when addresses are assigned without checking the block's boundaries first: a broadcast address handed to a device, two subnets overlapping, or a block too small for growth, usually after a rushed router change or an unrecorded manual assignment.
- Broadcast addresses handed out by mistake: the last address in a block is reserved. Give it to a device and that device cannot communicate normally.
- Overlapping ranges: two subnets sharing addresses cause intermittent failures that look like faulty hardware.
- Ranges too small for growth: a /28 gives only 14 usable addresses, so a few new staff and cameras soon force a full re-addressing.
- Ranges too large for control: a flat /24 mixes staff PCs, printers, cameras, and guests, making faults harder to isolate.
- Undocumented static addresses: an address assigned from memory gets assigned again by DHCP later, and two devices collide.
Calculating correctly does not fix all of these, but it removes the most common cause: not knowing where a block starts, ends, and how many usable addresses it contains.
How do you use the CodexFuse IP range calculator?
Use the tool by entering an IPv4 address and a CIDR prefix on the live tool page, then reading the network, broadcast, mask, and usable range it returns. The whole check takes under a minute, and you should record the result before configuring any device.
- Open the tool and enter the base address: go to the IP Range Calculator and type the IPv4 address you are planning around, for example 192.168.10.0.
- Enter the CIDR prefix: add the prefix length, such as 26 for a 64-address block. The prefix is the number after the slash in CIDR notation.
- Read the four outputs together: check the network address, the broadcast address, the subnet mask, and the usable range before you assign anything.
- Write the range down before configuring devices: record the network, broadcast, and usable range so the next person does not have to reverse-engineer your choices.
Always check the broadcast address first. If the address you planned to assign equals the broadcast address, or the network address, stop — neither can be assigned to a normal host device.
Worked example: a 25-person office plans a new subnet
Here is one complete example, end to end, with a clearly fictional office so you can follow every number.
The scenario. Harper & Lane, a fictional 25-person accountancy firm, is fitting out a new floor. It needs addresses for 25 staff PCs, 4 printers, 3 access points, 2 servers, and 6 cameras — 40 devices — plus room for about 15 more over two years, starting from 192.168.10.0.
The input. The IT lead enters 192.168.10.0 with a /26 prefix. A /26 holds 64 addresses, covering 40 devices today plus growth, without handing the floor a much larger block than needed.
The output. The tool returns the following block:
| Result | Value |
|---|---|
| Network address | 192.168.10.0 |
| Subnet mask | 255.255.255.192 |
| First usable address | 192.168.10.1 |
| Last usable address | 192.168.10.62 |
| Broadcast address | 192.168.10.63 |
| Total addresses | 64 |
| Usable addresses | 62 |
How the numbers are used. The gateway takes 192.168.10.1, servers take 192.168.10.2 and 192.168.10.3, printers take 192.168.10.10 to 192.168.10.13, DHCP hands out 192.168.10.20 to 192.168.10.50, and cameras take 192.168.10.51 to 192.168.10.56. Nothing touches 192.168.10.0 or 192.168.10.63.
The check that saved a second mistake. The IT lead also runs 192.168.10.64/26 and confirms its usable range is 192.168.10.65 to 192.168.10.126. The blocks do not overlap, so the neighbouring floor can use the second block later.
That is the point of calculating before configuring: the firm never touched a live router to learn that a /28 would have been too small.
Which CIDR size should you choose?
Choose CIDR size from device count plus headroom, not habit: count today's devices, add at least 30% for growth, then round up to the next block size. A /24 for everything mixes device types, while the tightest block guarantees a painful re-addressing later.
| CIDR | Total addresses | Usable hosts | Good fit for |
|---|---|---|---|
| /30 | 4 | 2 | A point-to-point link between two routers |
| /29 | 8 | 6 | A tiny device group, such as a server pair plus gateways |
| /28 | 16 | 14 | A small room or a single camera group |
| /27 | 32 | 30 | A small team or one department floor |
| /26 | 64 | 62 | A 25–40 device office with growth room |
| /25 | 128 | 126 | A larger office or a whole small site |
| /24 | 256 | 254 | A full site, or several grouped subnets under one plan |
A practical rule: count today's devices, add at least 30% headroom, then round up to the next block size. Re-addressing later costs far more than a few unused addresses now.
A calculated range is not a guarantee that those addresses are free. Check your router and DHCP server first: an address inside a valid range can still be in use by a device you forgot about.
How does this fit with CIDR and subnet planning?
A range calculator tells you what one block contains, while subnet planning tells you how to split a larger block into smaller ones without overlap. Use the range calculator to verify each resulting block after you have decided how to divide the larger address space.
If you already know your CIDR notation and want the full range it implies, start with the IP Range Calculator. If you are still deciding how to carve up a block, read our guide on turning CIDR notation into the full address range and our CIDR calculator walkthrough first, then come back and verify each resulting block here.
Two companion checks help alongside any range change: an IP address lookup to confirm an address's version and type, and an IP blacklist check on a public address before blaming your own network for a failure.
One wrong boundary can knock printers, cameras, and whole teams offline. Work out the exact usable range first — then let CodexFuse manage the hosting, email, security, and backups behind it, fully managed on pay-as-you-go credits, so you are not babysitting servers as well as subnets.
Get Started with CodexFuseWhat the IP range calculator does not do
A clean calculation can create false confidence, so note these limits.
- It does not scan your network: it calculates what a block contains, not which addresses are already in use live.
- It does not configure your router or DHCP server: you still apply the gateway, DHCP range, and reservations yourself.
- It does not handle IPv6: the tool page describes IPv4 only; IPv6 needs a dedicated tool.
- It does not design your segmentation: deciding which devices belong on which subnet is a security decision, not arithmetic.
- It does not replace a network audit: if addresses are colliding, reconcile correct ranges against a real device inventory before changing anything live.
If problems return after the ranges are correct — dropouts, devices vanishing after reboot — the cause is usually DHCP scope, DNS, cabling, or a failing switch, not the arithmetic.
When CodexFuse is the right next step
Many readers arrive here in the middle of a bigger move: a new office, a server migration, or the moment a business stops tolerating surprise bills and scattered subscriptions.
That is where CodexFuse fits as a concrete workflow. It is an all-in-one, fully managed IT service on credits: add credits and use managed hosting, business email, security, and backups from one place, without juggling subscriptions or babysitting servers. Move services one at a time — hosting first, then email, then backups — checking each works before moving the next.
The decision rule is simple: if your pain is too many vendors, too many bills, and nobody owning the setup, a managed all-in-one platform on credits removes that fragmentation. If it is one faulty switch, fix that device first.
Frequently Asked Questions
What is an IP range?
An IP range is the full set of addresses in one network block, from network address to broadcast address. Only addresses between those endpoints can normally be assigned.
How do I calculate an IP range from CIDR notation?
Enter the IPv4 address and CIDR prefix into an ip range calculator. It derives the mask, then returns the network, broadcast, and first and last usable addresses.
Why is the broadcast address not usable?
The broadcast address is reserved for messaging every device on that subnet at once. Assigning it to one device breaks normal communication.
How many usable addresses does a /26 block have?
A /26 block has 64 addresses and 62 usable hosts, because the network and broadcast addresses are reserved.
Can I use the IP range calculator for IPv6?
No. This tool works with IPv4 only; IPv6 uses a different format and needs a dedicated range tool.
Do I need an account to use the tool?
The tool page notes you need to log in, with a free account option. The calculation itself is free and unlimited once signed in.
