Simple IP Subnet Calculator (IPv4 & IPv6)
Type an IPv4 or IPv6 network like 192.168.1.10/24 or 2001:db8::/48, then click Calculate.
FAQ
What should I type?
Enter a network in CIDR form, like 192.168.1.10/24 or 2001:db8::/48.
What do I get back?
IPv4: network, mask, wildcard, broadcast, usable range, total & usable hosts.
IPv6: network, start–end range, and address count (shown as a power when huge).
Is it private?
Yes. Everything runs in your browser; nothing is uploaded.
Understanding IP Subnets (Beginner-Friendly Guide)
This short guide explains the terms you’ll see in the results and how to choose a subnet that fits your needs.
What is CIDR?
CIDR (Classless Inter-Domain Routing) writes a network as IP/prefix, for example 192.168.1.10/24 (IPv4) or 2001:db8::/48 (IPv6). The prefix tells you how many leading bits are the network part. The rest are host addresses.
IPv4 vs IPv6 at a glance
- IPv4: 32-bit addresses like 203.0.113.25. Has broadcast and “usable hosts”.
- IPv6: 128-bit addresses like 2001:db8::1. No broadcast (uses multicast instead). Enormous address space.
How usable hosts are calculated (IPv4)
For most prefixes, usable hosts = total addresses − 2 (you reserve the network and broadcast addresses). There are two special cases:
- /31: point-to-point links — both addresses are usable (no traditional broadcast).
- /32: a single host address.
Why you won’t see “broadcast” in IPv6
IPv6 does not use broadcast addresses. Instead, it relies on multicast groups. That’s why this calculator only shows the IPv6 network and its start–end range.
Choosing a prefix length
- Smaller prefix number (e.g., /16) → larger network, more hosts.
- Larger prefix number (e.g., /28) → smaller network, fewer hosts.
- IPv6 best practice: most LANs use /64; sites often receive /48 or /56.
Quick IPv4 reference
| Prefix | Subnet Mask | Usable Hosts | Total Addresses |
|---|---|---|---|
| /24 | 255.255.255.0 | 254 | 256 |
| /25 | 255.255.255.128 | 126 | 128 |
| /26 | 255.255.255.192 | 62 | 64 |
| /27 | 255.255.255.224 | 30 | 32 |
| /28 | 255.255.255.240 | 14 | 16 |
| /29 | 255.255.255.248 | 6 | 8 |
| /30 | 255.255.255.252 | 2 | 4 |
| /31 | 255.255.255.254 | 2* | 2 |
| /32 | 255.255.255.255 | 1* | 1 |
*Special cases: /31 point-to-point (2 usable), /32 single host.
Quick IPv6 reference
| Prefix | Addresses | Typical use |
|---|---|---|
| /48 | 280 | Large site allocation |
| /56 | 272 | Small site allocation |
| /64 | 264 | Standard LAN / SLAAC networks |
| /128 | 1 | Single interface address |
Examples
- IPv4 example: 192.168.1.10/24 → Network: 192.168.1.0, Broadcast: 192.168.1.255, Usable range: 192.168.1.1 – 192.168.1.254.
- IPv4 point-to-point: 203.0.113.0/31 → Two usable addresses: 203.0.113.0 and 203.0.113.1.
- IPv6 example: 2001:db8::/64 → Start: 2001:db8::, End: 2001:db8::ffff:ffff:ffff:ffff, Total: 264.
Common input issues (quick fixes)
- Missing “/prefix”. Always include it: IP/prefix.
- IPv4 octets out of range. Each must be 0–255 (e.g., 256 is invalid).
- Extra spaces or typos. Try pasting a clean value like 10.0.5.17/20 or 2001:db8::/48.
Need a quick test value? Try or .