CIDR / Subnet Calculator
Expand an IPv4 CIDR block into its network address, broadcast, netmask, wildcard, usable host range, and total address count.
CIDR / subnet calculator
Computes network and broadcast addresses, usable host range, mask, wildcard, and host count for an IPv4 CIDR. Pure client-side.
Why this is useful
CIDR arithmetic by hand is tedious and error-prone — and easy to get wrong in ways that silently break firewall rules, VPC peering, or routing tables. This calculator handles the ones engineers actually do every day:
- Is this IP inside this block? Compare against the network/broadcast range.
- How many addresses in a /22? The total and usable host counts come out directly.
- What’s the netmask for a /23? Shown in dotted decimal and wildcard form.
- Does this block overlap with that one? Calculate both sides and compare ranges.
Special cases
- /31 — two addresses, both usable (RFC 3021). Meant for point-to-point links.
- /32 — single host route. No network, no broadcast.
- /30 and smaller — the network and broadcast addresses are reserved; usable hosts = total − 2.
Privacy
Pure client-side math. Your input never leaves the browser.