IPv4 Calculator
Convert an IPv4 address between dotted, decimal, binary and hex, convert CIDR to a subnet mask, and see whether an address is private or reserved.
This address
- Dotted quad
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- Decimal
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- Hexadecimal
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- Binary
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- Class
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- Reverse DNS name
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Kind of address
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All Network tools →This tool runs entirely in your browser. Nothing you enter is sent to our servers, so there is nothing for us to store or see.
This tool reads public records — DNS, WHOIS and certificate data that registries and servers publish openly. It sends nothing to the host you enter and changes nothing there. Use it on infrastructure you own or are authorised to look into.
About the IPv4 Calculator
Convert a single IPv4 address between every form it turns up in — dotted quad, 32-bit decimal integer, hexadecimal and binary — and find out what kind of address it is.
Logs and databases store addresses in all of these. A firewall rule shows hex, an application log shows the integer, a packet capture shows binary, and working out which one you are looking at is half the job. Paste any of them and the tool works out the form for itself.
It also names the reserved ranges, which is the question behind most lookups: is this address routable on the internet, or is it private, loopback, link-local or carrier-grade NAT? The boundaries are exact, including the one people misremember — RFC 1918 gives 172.16.0.0/12, which ends at 172.31.255.255, so 172.32.0.1 is a public address. 169.254.169.254, the cloud metadata address, is correctly identified as link-local.
Subnet masks convert both ways, and a non-contiguous mask such as 255.255.0.255 is rejected with an explanation rather than silently accepted — every octet in it is legal, and it is still not a mask.
How to use the IPv4 Calculator
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Paste an address in any form
A dotted quad, a decimal integer or a hex value. The tool works out which it is rather than making you say.
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Read every representation
Dotted, decimal, hexadecimal and binary appear together, with the octets separated so you can read the bits that matter.
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Check what kind of address it is
Private, loopback, link-local, multicast, documentation or publicly routable — with the RFC that reserves it.
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Convert a mask or prefix
Enter a prefix length to get the subnet mask, or a mask to get the prefix. Invalid masks are rejected with the reason.
Frequently asked questions
Which IP ranges are private?
RFC 1918 reserves three: 10.0.0.0/8, 172.16.0.0/12 and 192.168.0.0/16. The middle one is the one people get wrong — it covers 172.16.0.0 to 172.31.255.255, not 172.16 to 172.32. RFC 6598 adds 100.64.0.0/10 for carrier-grade NAT, which is not private in the RFC 1918 sense but is not routable on the public internet either.
What is 169.254.169.254?
It is a link-local address, from the 169.254.0.0/16 block a host assigns itself when DHCP fails. That specific address is also the metadata endpoint on AWS, Azure and Google Cloud, which is why it appears so often in security advisories — a server-side request forgery that reaches it can read instance credentials.
Why is 255.255.0.255 not a valid subnet mask?
Because a mask has to be a run of ones followed by a run of zeros, with no gaps. That value is 11111111.11111111.00000000.11111111 — the ones are not contiguous. Every octet in it is a legal number, which is why tools that only validate the octets accept it and produce nonsense.
Are address classes still used?
No. Classful addressing was replaced by CIDR in 1993, and no router has made a routing decision based on class since. The class is reported here because it still appears in certification exams and older vendor documentation, but it tells you nothing about how an address is actually routed today.
Is anything sent to a server?
No. All the arithmetic happens in your browser. Nothing about the addresses you look up is transmitted or logged, which matters when the address in question is on your own network.