Subnet Calculator
CIDR /prefix → mask and host count. Click any i for detail.
IPv4
Prefix length
i
Prefix
0–32. /24 is 255.255.255.0. |
|
|---|---|
IP address (optional)
i
IP
Used to compute network and broadcast. Example 192.168.1.10. |
How to use this calculator
- Enter CIDR prefix length 0–32.
- Optional: enter an IPv4 host address.
- Read subnet mask, wildcard, usable hosts.
- See network and broadcast when an IP is provided.
Results explained
/24 is 255.255.255.0 with 254 usable hosts on classic LANs. /31 and /32 use special host counts for point links.
Quick reference: IPv4 CIDR
/24 → mask 255.255.255.0, 254 usable hosts.
| Item | Detail |
|---|---|
| /8 | 255.0.0.0 · huge networks |
| /16 | 255.255.0.0 · 65,534 hosts |
| /24 | 255.255.255.0 · 254 hosts |
| /32 | single host |
IPv6 is not on this page.
How the estimate is built
hosts = 2^(32−prefix) − 2 (except /31=2, /32=1 special cases).
Example scenario
/24 → mask 255.255.255.0, 254 usable hosts.
FAQ
Why does /31 show 2 hosts?
RFC 3021 allows point-to-point links with no broadcast waste.
Can I paste IPv6?
No. This calculator is IPv4 only.
Is wildcard the inverse mask?
Yes for ACL math: wildcard bits are don't-care positions.