CIDR Subnet Calculator
Enter an IPv4 CIDR block and get the full subnet breakdown: mask, wildcard, range, broadcast, and usable hosts.
Enter network values
Use the example or enter your own subnet, plan, MAC, or port value.
Results update locally in your browser.
Enter an IPv4 CIDR block or host address with prefix. The calculator shows the network, broadcast, subnet mask, wildcard mask, and usable range.
Address range details
A subnet worksheet with bit boundary, common split comparison, usable hosts, and reserved/private context.
254 usable out of 256 total addresses.
192.168.1.0/24 is the common small-network default with 254 usable hosts.
Next: Reserve gateway, infrastructure, printer, and static addresses before sizing the DHCP scope.
RFC 1918 private 192.168.0.0/16
Gateway candidate: 192.168.1.1
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| Mask bits | 111111111111111111111111|00000000 |
|---|---|
| Boundary | 24 network bits · 8 host bits |
| Network address | 192.168.1.0 |
|---|---|
| Broadcast address | 192.168.1.255 |
| Full IP range | 192.168.1.0 – 192.168.1.255 |
| Wildcard mask | 0.0.0.255 |
| Binary mask | 11111111.11111111.11111111.00000000 |
| Total addresses | 256 |
| Prefix | Mask | Total | Usable | Range | Typical fit |
|---|---|---|---|---|---|
| 192.168.1.0/24 | 255.255.255.0 | 256 | 254 | 192.168.1.0 – 192.168.1.255 | small LAN / full VLAN |
| 192.168.1.0/25 | 255.255.255.128 | 128 | 126 | 192.168.1.0 – 192.168.1.127 | split LAN into two halves |
| 192.168.1.0/26 | 255.255.255.192 | 64 | 62 | 192.168.1.0 – 192.168.1.63 | four smaller segments from a /24 |
RFC/private/reserved context
- RFC 1918 private ranges are 10.0.0.0/8, 172.16.0.0/12, and 192.168.0.0/16.
- Special-use ranges include loopback 127.0.0.0/8, link-local 169.254.0.0/16, CGNAT 100.64.0.0/10, multicast 224.0.0.0/4, and documentation TEST-NET ranges.
- Private/reserved context does not prove reachability or ownership; verify routing, NAT, firewall, and VPN selectors.
Notes
These are planning and conversion utilities. Confirm production network changes against your router, firewall, cloud provider, and ISP requirements before applying them.
Use the CIDR Subnet Calculator without guessing what to do next
- Start with the example values to see what the main result looks like.
- Replace the example values with the best numbers you have right now; rough estimates are fine for a first pass.
- Change one input at a time so you can see which assumption actually moves the answer.
What the result means
The result turns network notation into something easier to read: ranges, host counts, masks, wildcard masks, ports, or planning blocks.
How to use it
Use the output to plan or double-check, then compare it with the real network before changing a route, VLAN, DHCP scope, firewall rule, or ACL.
What can change it
A valid network number can still be wrong for your environment if it overlaps, conflicts with routing, exposes traffic, or breaks change-control rules.
Good for
Decode a CIDR block.
Check this next
Try IP Address + Subnet Mask Calculator, Subnet Mask to CIDR Converter, Subnet Splitter Calculator to cross-check the same decision from another angle.
Best habit
Run a conservative case and an optimistic case. The gap between them is often more useful than a single answer.
Common uses
- Decode a CIDR block.
- Find usable host range.
- Check network and broadcast addresses.
Common questions
Is the CIDR Subnet Calculator private?
CalcShelf calculators run without an account. Your entries stay in the calculator while you work; CalcShelf does not save them or place your numbers in shareable links.
How accurate is the CIDR Subnet Calculator?
It follows common IPv4, CIDR, mask, range, and port conventions. Production networks still need live-config, routing, ACL, overlap, and change-control review.
What should I check after using the CIDR Subnet Calculator?
Verify live allocations, overlaps, gateway conventions, routes, ACL/firewall order, documentation, and rollback plan before production changes.
Which calculator should I try next?
Try IP Address + Subnet Mask Calculator, Subnet Mask to CIDR Converter, Subnet Splitter Calculator as next checks so you can compare the same decision from another angle before acting.
Method behind the estimate
Networking tools use IPv4, CIDR, subnet mask, wildcard mask, range, VLAN, DHCP, and port-reference rules for planning and sanity checks.
Why the detail matters
Before changing production routing, firewall, VLAN, DHCP, or address plans, verify against the actual network, documentation, and change-control process.
No account or saved inputs
Your calculator values are for your session. CalcShelf does not require an account, save calculator entries, or add your numbers to shareable URLs.
Copy or print safely
Use any copy, print, or worksheet controls as local handoff tools for your own notes, supplier calls, lender questions, or implementation checklist. They are there to help you explain the result to a human.
Before acting
Treat the result as a decision draft, not a verdict. Recheck the source numbers, run a downside case, and verify the real-world rule, quote, label, or spec that controls the final answer.
Last reviewed: May 11, 2026. See methodology and editorial policy for formulas, assumptions, rounding, review approach, and limitations. For network changes, verify against live configuration, vendor docs, and change-control requirements.