Visual Subnet Calculator
Plan IPv4 subnets visually. Enter a network, then split it into smaller subnets or join them back, and watch the bits, address ranges, and host counts update as you go.
| Subnet | Netmask | Usable range | Hosts | Split / Join |
|---|
0 subnets covering 256 addresses. Hover a block for its range.
Recommended Settings
Pro Tips
- •Split only the subnets you need to divide. Leaving some larger while shrinking others is how you give different sites different sizes (VLSM)
- •Usable hosts is the block size minus the network and broadcast addresses, so a /24 has 254 and a /30 has 2
- •Join is available when two halves of the same parent are both present, mirroring how you would merge them back
- •Use the evenly-split option to carve one block into equal subnets in a single step, then adjust individual rows
- •Copy table pastes straight into a spreadsheet, and CSV downloads the whole plan
Most Popular
Most people start with a /24 such as 192.168.0.0/24 or 10.0.0.0/16 and split it for different departments or sites
When to Use This Tool
Lay out address ranges for VLANs, offices, or cloud subnets before you configure anything.
Carve one allocation into right-sized pieces for branches that need different numbers of hosts.
See exactly how borrowing host bits creates subnets, with the binary shown next to the result.
Confirm that planned subnets don't overlap and that each has enough usable addresses.
How It Works
Enter a network in CIDR form, like 192.168.0.0/24
Press Split on any subnet to cut it into two equal halves, or choose an even split for the whole block
Press Join to merge two matching halves back together
Read off each subnet's mask, usable range, and host count, then copy or download the plan
100% Private
Files never leave your device. All processing happens locally in your browser.
Lightning Fast
Powered by Client-side IPv4 arithmetic for optimal performance on modern browsers.
Open Source
Built with verified, open-source libraries. Fully transparent.
Frequently Asked Questions
What is a visual subnet calculator?
It lets you divide a network into subnets by clicking, rather than working out masks by hand. Each split halves a subnet and shows its new address range, mask, and host count, so you can see how an address block is carved up.
How do I split a subnet?
Enter a network such as 192.168.0.0/24 and press Split next to a subnet. A /24 becomes two /25s, each with 126 usable hosts. Split any resulting subnet again to keep going, down to /30.
What do the coloured bits mean?
The 32 bits of the address are shown in four groups of eight. Blue bits are the network, amber bits are the extra bits your splits borrow to make subnets, and grey bits are what's left for hosts. Splitting moves bits from grey to amber.
Can I make subnets of different sizes?
Yes. Split only the subnets you want to make smaller and leave the rest. Mixing sizes like this is called variable length subnet masking (VLSM), and it avoids wasting addresses on small sites.
How is this different from the IPv4 Subnet Calculator?
The IPv4 Subnet Calculator gives the details of one network at a time. This tool is for planning: it splits and joins a block into many subnets and keeps the whole layout in view.
Why can't I split below /30?
A /30 holds four addresses, two of them usable, which is the smallest subnet with a network and broadcast address. Smaller blocks, /31 and /32, are special cases used for point-to-point links and single hosts.
Is my data sent to a server?
No. All the calculations happen in your browser, so your network plans stay on your device.