| Subnet name | Hosts needed | |
|---|---|---|
| Subnet | CIDR | Mask | Network | Host range | Broadcast | Usable |
|---|---|---|---|---|---|---|
| Wi-Fi | 192.168.1.0/25 | 255.255.255.128 | 192.168.1.0 | 192.168.1.1 – 192.168.1.126 | 192.168.1.127 | 126 |
| Sales | 192.168.1.128/26 | 255.255.255.192 | 192.168.1.128 | 192.168.1.129 – 192.168.1.190 | 192.168.1.191 | 62 |
| Engineering | 192.168.1.192/27 | 255.255.255.224 | 192.168.1.192 | 192.168.1.193 – 192.168.1.222 | 192.168.1.223 | 30 |
| Servers | 192.168.1.224/28 | 255.255.255.240 | 192.168.1.224 | 192.168.1.225 – 192.168.1.238 | 192.168.1.239 | 14 |
Largest-first allocation (standard VLSM), minimum /30 per subnet. Single-subnet calculator →
Related tools
Free, and they run in your browser — nothing you enter is sent to us or stored.
- CIDR CalculatorCIDR ↔ subnet mask ↔ address range ↔ host count, with the bit-level breakdown.
- IPv6 Subnet CalculatorCompress/expand (RFC 5952), prefix maths, /64 counts and scope for IPv6.
- IP Address ConverterDotted ↔ integer ↔ hex ↔ binary, with public/private scope detection.
- Subnet Cheat SheetEvery CIDR prefix → mask, wildcard, usable hosts and total addresses, in one table.
VLSM — common questions
What is VLSM?
Variable Length Subnet Masking lets you carve a single network into subnets of different sizes, instead of forcing every subnet to the same mask. A 50-host LAN gets a /26, a point-to-point link gets a /30, and so on — so you waste far fewer addresses than fixed-length subnetting.
How does this VLSM calculator allocate subnets?
It sorts your required subnets largest-first, gives each the smallest standard block that fits its host count (block = next power of two ≥ hosts + 2, minimum /30), and places them sequentially from the base network so they stay aligned with no gaps. It shows each subnet’s CIDR, mask, network, host range, broadcast and usable count, plus how much of the pool you used.
Why largest-first?
Allocating the biggest subnets first keeps every block aligned on its natural boundary, which avoids fragmentation and wasted space. If a requirement doesn’t fit the base network, the calculator tells you which one overflowed so you can pick a larger pool.
Can Servnet help with the real network?
Yes — we design and deliver enterprise IP addressing, segmentation, switching and routing on Cisco, HPE Aruba, Juniper and Fortinet. Plan the addressing here, then talk to us about the build.
Talk to a UK specialist
Get expert advice or a no-obligation quote — servers, storage, networking, maintenance, finance and cloud. We reply the same working day.