CIDR / IP Range Calculator
CIDR to IP range calculator — type any IPv4 CIDR block like 10.0.0.0/22 to instantly see the first and last usable host, network and broadcast addresses, subnet and wildcard masks, total and usable host counts, class and public/private scope. Runs entirely in your browser.
CIDR / IP Range Calculator
How to Use the CIDR Range Calculator
Type a CIDR block
Enter an address and prefix, like 10.0.0.0/22.
Read the range
See the first and last usable host instantly.
Check the masks
Grab the subnet and wildcard masks for your config.
Confirm scope
See the class and whether the block is private or public.
From CIDR Block to Concrete Range
Classless Inter-Domain Routing — CIDR — is the notation that quietly runs the modern internet. Introduced in 1993 to replace the wasteful Class A/B/C system, it writes a network as an address and a prefix length, like 192.168.1.0/24, where the prefix states how many leading bits belong to the network. That compact form is everywhere: in routing tables, firewall rules, cloud security groups and allowlists. The trouble is that a human reading “/22” cannot instantly see which addresses it covers. This calculator does the translation for you, turning any IPv4 CIDR block into the concrete range of addresses it represents.
Enter a block and it derives everything by applying the prefix as a bitmask. Setting all the host bits to zero gives the network address; setting them all to one gives the broadcast address; the usable host range sits between the two, so a /24 runs from .1 to .254. It also reports the subnet mask and its inverse, the wildcard mask — the form Cisco access control lists expect — along with the total address count, the usable host count, the legacy class, and whether the block falls inside the private RFC 1918 ranges or is publicly routable. Two special cases are handled correctly: a /32 is a single host, and a /31 is a two-address point-to-point link under RFC 3021 where both addresses are usable.
The practical value is in writing and checking rules without arithmetic mistakes. When you allowlist a partner’s /28 or document a cloud subnet’s range, getting the first and last address exactly right matters — an off-by-one error can expose or lock out a host. Because each decrease of the prefix doubles the block and each increase halves it, the size grows quickly, and seeing the total alongside the range helps you sanity-check that a block is as large as you intended. Everything is computed locally in your browser using 32-bit integer maths, so internal ranges and infrastructure details never leave your device. Treat the output as a fast, reliable reference, and confirm anything safety-critical against your authoritative network documentation.
An off-by-one in a firewall range can expose or strand a host — converting CIDR to an exact range removes the guesswork.
10 Facts About CIDR
CIDR replaced the old Class A/B/C system in 1993.
The /24 block holds 256 addresses, 254 usable.
Each step down (e.g. /24 → /23) doubles the block.
Network and broadcast addresses can’t be hosts.
A /31 is allowed for point-to-point links (RFC 3021).
A /32 describes a single host address.
The wildcard mask is the inverse of the subnet mask.
ACLs and firewalls often use wildcard masks.
10/8, 172.16/12 and 192.168/16 are private ranges.
This calculator runs in your browser — nothing is uploaded.
Frequently Asked Questions
- CIDR (Classless Inter-Domain Routing) notation writes a network as an address followed by a slash and a prefix length, such as 192.168.1.0/24. The prefix says how many leading bits are fixed for the network; the rest are available for hosts. It replaced the rigid Class A/B/C scheme in 1993 and lets networks be sized far more flexibly.
- It applies the prefix as a bitmask to the address to find the network address (all host bits zero) and the broadcast address (all host bits one). The first usable host is one above the network address and the last is one below the broadcast, so a /24 gives a usable range from .1 to .254. It also reports the masks, counts, class and scope.
- In a normal subnet the first address is reserved as the network identifier and the last as the broadcast address, neither of which can be assigned to a device. So a /24 has 256 total addresses but 254 usable. The exceptions are /31 links and /32 hosts, which this tool handles separately.
- A wildcard mask is the bitwise inverse of the subnet mask: where the subnet mask has 1s, the wildcard has 0s, and vice versa. For a /24, the subnet mask is 255.255.255.0 and the wildcard is 0.0.0.255. Cisco access control lists and some routing configurations specify ranges using wildcard masks rather than subnet masks, so seeing both is handy.
- A /32 identifies a single host — one exact address — and is common in host routes and firewall rules. A /31 defines a two-address block intended for point-to-point links under RFC 3021, where the usual network and broadcast reservations are waived so both addresses are usable. This calculator reflects those special cases in the usable-host count.
- Private IPv4 ranges, defined by RFC 1918, are 10.0.0.0/8, 172.16.0.0/12 and 192.168.0.0/16, plus loopback (127.0.0.0/8) and link-local (169.254.0.0/16). The tool labels the block accordingly. Private addresses are not routable on the public internet and are typically used behind NAT.
- They overlap, but this tool is oriented around converting a CIDR block into the concrete IP range it covers — the first and last usable addresses and total counts — which is what you need when writing firewall rules, allowlists or documentation. A classic subnet calculator emphasises dividing a network into subnets. Use whichever framing fits your task.
- The total is two to the power of the host bits, which is 32 minus the prefix. A /24 leaves 8 host bits, so 2⁸ = 256 addresses; a /22 leaves 10 bits, so 1,024. Each time you decrease the prefix by one, the block doubles in size; each time you increase it, the block halves.
- No. All the arithmetic runs in JavaScript on your device. Nothing you type is transmitted, logged or stored, so the tool is safe to use with internal network ranges and sensitive infrastructure details.
- Completely free, with no account or limit. It works offline once the page has loaded and collects no data.
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