IPv4 subnet calculator
Split an IPv4 network into smaller prefixes in your browser. Lists up to 256 subnets. Nothing is uploaded.
IPv4 only. Calculate in this tab.
How to use the IPv4 subnet calculator
- Enter the parent CIDR (for example 10.0.0.0/24).
- Set the new prefix (26 splits a /24 into four /26s).
- Copy the list. A shorter new prefix supernets instead of splitting.
Equal slices
Each child has the same prefix length. The page lists network and broadcast per slice, capped at 256 rows so a /8→/24 does not freeze the tab. For the parent’s own mask and hosts, use the CIDR calculator.
Nothing is uploaded
The list is local.
IPv4 subnet calculator FAQ
Need a VLSM mix?
This page is equal-length splits. Plan leftover space by hand.
Why a cap?
65536 rows would hang a browser. Copy a /16 parent if you need the next 256 /24s.