Online IPv4 CIDR calculator: input IP/prefix (e.g., 192.168.1.0/24) to calculate network address, broadcast address, subnet mask, host range, and total hosts. Essential for network engineers.
TL;DR: Free online IPv4 CIDR subnet calculator. Input IP and prefix to compute network address, broadcast, subnet mask, host range, and available hosts. Runs locally in browser.
For local tools, open DevTools → Network and search your input — it should not appear in requests.
Usage Guide
Expand IPv4 CIDR details or cover a start–end range with minimal CIDR blocks — local.
1. Expand CIDR
Host bits are normalized to the network address.
- Use CIDR→details mode.
- Enter a prefix or pick an example.
- Copy network, broadcast, mask, hosts.
2. Range→CIDR
Blocks are alignment-minimal; invalid ranges error aloud.
- Switch modes.
- Enter start and end IPv4.
- Read the covering blocks.
3. Prefix intuition
Longer prefix, smaller range; /31 and /32 are special.
4. Traps
- Cloud reserves lower usable counts.
- Normalize before pasting into ACLs.
- IPv4 only here.
5. Vs subnet tool
Size and cover here; equal splits there.
6. Before change
Missing one covering block leaves a hole.
- Copy three columns into the change ticket.
- Recheck broadcast vs host.
- Ship full covering sets.
7. Reminder
Local math only — verify against your cloud console fields.
FAQ
CIDR→details mode takes an IP/prefix (e.g. 192.168.1.0/24) and computes the network address, broadcast address, netmask, usable host range, and host count. Range→CIDR mode covers an inclusive IPv4 start–end span with as few CIDR blocks as practical — handy for firewall rules and route aggregation.
The tool normalizes to the network address per the netmask before displaying: 10.0.0.15/24 corresponds to network 10.0.0.0/24. When security-group or routing-table entries mix host and network addresses, check the normalized result before pasting. In range mode, reversed or invalid start/end addresses raise an explicit error instead of being silently swapped.
Normally 2 to the power of (32 − prefix), minus two for the network and broadcast addresses: /24 yields about 254 hosts, /16 about 65 thousand, /8 about 16 million. /31 and /32 are exceptions — point-to-point links and single hosts — where the minus-two rule does not apply. Cloud planning also needs headroom, since providers reserve gateway and other addresses, leaving fewer usable hosts than the math suggests.
The current version focuses on IPv4 (detail expansion and range covering); copying results into IPv6 planning will misfire. For IPv6, use a dedicated tool or your cloud console calculator.
This page answers "how big is this block, what is its range, and how do I cover a start–end span"; the subnet calculator answers "how do I slice a large block into equal subnets". The usual order is to settle the overall block and boundaries here, then split it with the subnet tool. One more note: multi-block range-cover results must be deployed as a whole set — missing one block leaves part of the range unreachable.
No. All computation happens browser-side with nothing sent back, so intranet addresses and private ranges are safe to paste here.
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