Subnet Calculator
Split an IPv4 network into subnets by number of subnets, hosts per subnet, or VLSM per team. Table of networks, host ranges, broadcast and masks, CSV download.
How to split a network into subnets
- Enter the network to split, for example 192.168.10.0/24.
- Pick how to split it: by number of subnets, by hosts per subnet, or VLSM when each group needs a different size (one group per line, such as Sales: 60).
- The table appears right below; press "Download CSV" to open it in Excel.
Frequently asked questions
Each halving doubles the number of subnets, so the count is always 2, 4, 8, 16… The tool picks the smallest that is enough; the extra subnets can be kept for later.
VLSM means subnets of different sizes: a 60-device team gets a /26, a 12-device one a /28, a link between two routers a /30, so fewer addresses go to waste. The tool places the largest first so subnets sit side by side, and lists the space left.
Each subnet loses 2 addresses to the network and broadcast addresses, so a /26 has 64 addresses but 62 hosts. Needing 60 or 62 hosts gives a /26; 63 needs a /25.
Only IPv4 for now. In IPv6 each network is usually a /64 and you only count networks; the CIDR Calculator shows any single block.
The CIDR Calculator describes one address block. The Subnet Calculator takes one large network, splits it into many smaller ones and lists each of them.
It is completely free and needs no sign-up.
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