# SubnetKit

> A fast, clean, free subnet calculator and networking reference for sysadmins and developers. Every calculation runs client-side in the browser; nothing is uploaded. No sign up, no limits.

SubnetKit answers subnet and networking questions instantly: network and broadcast addresses, usable host ranges, subnet and wildcard masks, binary, CIDR expansion, IPv6 subnetting, IP base conversion, MAC formatting, and a reference page per CIDR prefix and per well-known port. It also offers a free keyless JSON API and an embeddable calculator widget.

## Core pages
- [Subnet calculator (home)](https://subnetkit.dev/): live IPv4 subnet calculator with mask, wildcard, and binary.
- [All tools](https://subnetkit.dev/tools): every calculator in one place.
- [CIDR cheat sheet](https://subnetkit.dev/cidr): every prefix /0 to /32 with mask, wildcard, and host count.
- [Port numbers](https://subnetkit.dev/port): common TCP and UDP ports and what they do.
- [Well-known port ranges](https://subnetkit.dev/port/well-known-ports): the 0 to 65535 port space explained.
- [Subnet by host count](https://subnetkit.dev/hosts): reverse lookup from a host count to the smallest CIDR block that fits it.
- [Free JSON API](https://subnetkit.dev/api): keyless CIDR and port lookups, no rate limits.
- [Embed widget](https://subnetkit.dev/embed): a free iframe subnet calculator for any site.

## Calculators
- [CIDR calculator](https://subnetkit.dev/cidr-calculator): Free CIDR calculator. Turn any CIDR block into its first and last IP, mask, and host count instantly. No sign up, runs in your browser.
- [Subnet mask calculator](https://subnetkit.dev/subnet-mask-calculator): Convert between prefix length and subnet mask instantly. See the wildcard mask and host count for any /0 to /32. Free and browser based.
- [Wildcard mask calculator](https://subnetkit.dev/wildcard-mask-calculator): Convert a subnet mask to its wildcard mask for Cisco access lists, and back. Instant, free, and runs entirely in your browser.
- [Supernet calculator](https://subnetkit.dev/supernet-calculator): Aggregate several CIDR blocks into the smallest single covering prefix. Free route summarization for cleaner routing tables. Runs in-browser.
- [IPv6 subnet calculator](https://subnetkit.dev/ipv6-subnet-calculator): Free IPv6 subnet calculator. Expand, compress, and subnet any IPv6 prefix. See the network, range, and address type instantly in your browser.
- [IP converter](https://subnetkit.dev/ip-converter): Convert an IPv4 address to a 32-bit integer, binary, hexadecimal, and octal, and back. Free IP address calculator that runs in your browser.
- [MAC address formatter](https://subnetkit.dev/mac-address-format): Reformat a MAC address between colon, dash, Cisco dotted, and bare forms. See the OUI and unicast bits. Free, instant, browser based.
- [Random IP generator](https://subnetkit.dev/random-ip): Generate random valid IPv4 addresses for testing, public or private. Free random IP generator that runs entirely in your browser.

## Guides
- [What is a subnet?](https://subnetkit.dev/guide/what-is-a-subnet): A subnet is a slice of a larger network. Learn what subnetting does, why it exists, and how to read a subnet, with worked examples. Free calculator included.
- [What is a subnet mask?](https://subnetkit.dev/guide/what-is-a-subnet-mask): A subnet mask marks which part of an IP is the network and which is the host. Learn to read masks like 255.255.255.0 and convert them to a prefix. Free tool.
- [What is CIDR notation?](https://subnetkit.dev/guide/what-is-cidr): CIDR replaces old address classes with a flexible prefix like /24. Learn how CIDR notation works, why it exists, and how to read a CIDR block. Free calculator.
- [VLAN vs subnet: what is the difference?](https://subnetkit.dev/guide/vlan-vs-subnet): A VLAN is a layer-2 broadcast domain; a subnet is a layer-3 address range. Learn how they relate, why they usually pair up, and when they do not. Clear guide.
- [Subnet masks worth memorising](https://subnetkit.dev/guide/subnet-cheat-sheet): The subnet masks worth memorising: mask, wildcard, and host count for each prefix from /8 to /32, plus the handful of numbers that cover most daily work.
- [How to calculate a subnet mask](https://subnetkit.dev/guide/how-to-calculate-a-subnet-mask): A step-by-step method for calculating a subnet mask from a host count, with a full worked example. No memorising required, just four short steps.
- [Classful vs classless addressing](https://subnetkit.dev/guide/classful-vs-classless-addressing): Classful addressing split IPv4 into fixed class A, B, and C networks. CIDR replaced it with classless, variable-length prefixes. What changed, and why it still matters.
- [Private vs public IP addresses](https://subnetkit.dev/guide/private-vs-public-ip-addresses): Private IP addresses only work on your own network; public ones are routable on the internet. The RFC 1918 ranges, why they exist, and how NAT connects them.

## CIDR prefix pages
Each prefix has its own page with a live calculator and worked example:
- [/0 subnet](https://subnetkit.dev/cidr/0)
- [/1 subnet](https://subnetkit.dev/cidr/1)
- [/2 subnet](https://subnetkit.dev/cidr/2)
- [/3 subnet](https://subnetkit.dev/cidr/3)
- [/4 subnet](https://subnetkit.dev/cidr/4)
- [/5 subnet](https://subnetkit.dev/cidr/5)
- [/6 subnet](https://subnetkit.dev/cidr/6)
- [/7 subnet](https://subnetkit.dev/cidr/7)
- [/8 subnet](https://subnetkit.dev/cidr/8)
- [/9 subnet](https://subnetkit.dev/cidr/9)
- [/10 subnet](https://subnetkit.dev/cidr/10)
- [/11 subnet](https://subnetkit.dev/cidr/11)
- [/12 subnet](https://subnetkit.dev/cidr/12)
- [/13 subnet](https://subnetkit.dev/cidr/13)
- [/14 subnet](https://subnetkit.dev/cidr/14)
- [/15 subnet](https://subnetkit.dev/cidr/15)
- [/16 subnet](https://subnetkit.dev/cidr/16)
- [/17 subnet](https://subnetkit.dev/cidr/17)
- [/18 subnet](https://subnetkit.dev/cidr/18)
- [/19 subnet](https://subnetkit.dev/cidr/19)
- [/20 subnet](https://subnetkit.dev/cidr/20)
- [/21 subnet](https://subnetkit.dev/cidr/21)
- [/22 subnet](https://subnetkit.dev/cidr/22)
- [/23 subnet](https://subnetkit.dev/cidr/23)
- [/24 subnet](https://subnetkit.dev/cidr/24)
- [/25 subnet](https://subnetkit.dev/cidr/25)
- [/26 subnet](https://subnetkit.dev/cidr/26)
- [/27 subnet](https://subnetkit.dev/cidr/27)
- [/28 subnet](https://subnetkit.dev/cidr/28)
- [/29 subnet](https://subnetkit.dev/cidr/29)
- [/30 subnet](https://subnetkit.dev/cidr/30)
- [/31 subnet](https://subnetkit.dev/cidr/31)
- [/32 subnet](https://subnetkit.dev/cidr/32)

## Host count pages
Reverse lookup: start from a host count and get the smallest CIDR block that fits it:
- [Subnet for 2 hosts](https://subnetkit.dev/hosts/2)
- [Subnet for 5 hosts](https://subnetkit.dev/hosts/5)
- [Subnet for 6 hosts](https://subnetkit.dev/hosts/6)
- [Subnet for 10 hosts](https://subnetkit.dev/hosts/10)
- [Subnet for 14 hosts](https://subnetkit.dev/hosts/14)
- [Subnet for 20 hosts](https://subnetkit.dev/hosts/20)
- [Subnet for 25 hosts](https://subnetkit.dev/hosts/25)
- [Subnet for 30 hosts](https://subnetkit.dev/hosts/30)
- [Subnet for 50 hosts](https://subnetkit.dev/hosts/50)
- [Subnet for 62 hosts](https://subnetkit.dev/hosts/62)
- [Subnet for 75 hosts](https://subnetkit.dev/hosts/75)
- [Subnet for 100 hosts](https://subnetkit.dev/hosts/100)
- [Subnet for 126 hosts](https://subnetkit.dev/hosts/126)
- [Subnet for 150 hosts](https://subnetkit.dev/hosts/150)
- [Subnet for 200 hosts](https://subnetkit.dev/hosts/200)
- [Subnet for 250 hosts](https://subnetkit.dev/hosts/250)
- [Subnet for 254 hosts](https://subnetkit.dev/hosts/254)
- [Subnet for 500 hosts](https://subnetkit.dev/hosts/500)
- [Subnet for 1000 hosts](https://subnetkit.dev/hosts/1000)
- [Subnet for 2000 hosts](https://subnetkit.dev/hosts/2000)
- [Subnet for 5000 hosts](https://subnetkit.dev/hosts/5000)
- [Subnet for 10000 hosts](https://subnetkit.dev/hosts/10000)
- [Subnet for 20000 hosts](https://subnetkit.dev/hosts/20000)
- [Subnet for 65534 hosts](https://subnetkit.dev/hosts/65534)

## Port categories
- [File transfer ports](https://subnetkit.dev/port/category/file-transfer)
- [Remote access ports](https://subnetkit.dev/port/category/remote-access)
- [Email ports](https://subnetkit.dev/port/category/email)
- [Core services ports](https://subnetkit.dev/port/category/core-services)
- [Web ports](https://subnetkit.dev/port/category/web)
- [Authentication ports](https://subnetkit.dev/port/category/authentication)
- [Windows ports](https://subnetkit.dev/port/category/windows)
- [Management ports](https://subnetkit.dev/port/category/management)
- [Databases ports](https://subnetkit.dev/port/category/databases)
- [Legacy protocols ports](https://subnetkit.dev/port/category/legacy-protocols)
- [Routing ports](https://subnetkit.dev/port/category/routing)
- [Printing ports](https://subnetkit.dev/port/category/printing)
- [Chat & messaging ports](https://subnetkit.dev/port/category/chat-and-messaging)
- [VoIP & streaming ports](https://subnetkit.dev/port/category/voip-and-streaming)
- [IoT & automation ports](https://subnetkit.dev/port/category/iot-and-automation)
- [Version control ports](https://subnetkit.dev/port/category/version-control)
- [Infrastructure & orchestration ports](https://subnetkit.dev/port/category/infrastructure-and-orchestration)
- [Message queues ports](https://subnetkit.dev/port/category/message-queues)
- [Gaming ports](https://subnetkit.dev/port/category/gaming)
- [Proxy & tunneling ports](https://subnetkit.dev/port/category/proxy-and-tunneling)

## Port pages
- [Port 7 (Echo)](https://subnetkit.dev/port/7)
- [Port 9 (Discard)](https://subnetkit.dev/port/9)
- [Port 13 (Daytime)](https://subnetkit.dev/port/13)
- [Port 17 (QOTD)](https://subnetkit.dev/port/17)
- [Port 19 (Chargen)](https://subnetkit.dev/port/19)
- [Port 20 (FTP-DATA)](https://subnetkit.dev/port/20)
- [Port 21 (FTP)](https://subnetkit.dev/port/21)
- [Port 22 (SSH)](https://subnetkit.dev/port/22)
- [Port 23 (Telnet)](https://subnetkit.dev/port/23)
- [Port 25 (SMTP)](https://subnetkit.dev/port/25)
- [Port 37 (Time Protocol)](https://subnetkit.dev/port/37)
- [Port 43 (WHOIS)](https://subnetkit.dev/port/43)
- [Port 53 (DNS)](https://subnetkit.dev/port/53)
- [Port 67 (DHCP)](https://subnetkit.dev/port/67)
- [Port 68 (DHCP client)](https://subnetkit.dev/port/68)
- [Port 69 (TFTP)](https://subnetkit.dev/port/69)
- [Port 70 (Gopher)](https://subnetkit.dev/port/70)
- [Port 79 (Finger)](https://subnetkit.dev/port/79)
- [Port 80 (HTTP)](https://subnetkit.dev/port/80)
- [Port 88 (Kerberos)](https://subnetkit.dev/port/88)
- [Port 109 (POP2)](https://subnetkit.dev/port/109)
- [Port 110 (POP3)](https://subnetkit.dev/port/110)
- [Port 111 (RPCbind)](https://subnetkit.dev/port/111)
- [Port 113 (Ident)](https://subnetkit.dev/port/113)
- [Port 115 (SFTP (legacy))](https://subnetkit.dev/port/115)
- [Port 119 (NNTP)](https://subnetkit.dev/port/119)
- [Port 123 (NTP)](https://subnetkit.dev/port/123)
- [Port 135 (MS-RPC)](https://subnetkit.dev/port/135)
- [Port 137 (NetBIOS-NS)](https://subnetkit.dev/port/137)
- [Port 138 (NetBIOS-DGM)](https://subnetkit.dev/port/138)
- [Port 139 (NetBIOS-SSN)](https://subnetkit.dev/port/139)
- [Port 143 (IMAP)](https://subnetkit.dev/port/143)
- [Port 161 (SNMP)](https://subnetkit.dev/port/161)
- [Port 162 (SNMP-TRAP)](https://subnetkit.dev/port/162)
- [Port 179 (BGP)](https://subnetkit.dev/port/179)
- [Port 194 (IRC)](https://subnetkit.dev/port/194)
- [Port 389 (LDAP)](https://subnetkit.dev/port/389)
- [Port 427 (SLP)](https://subnetkit.dev/port/427)
- [Port 443 (HTTPS)](https://subnetkit.dev/port/443)
- [Port 445 (SMB)](https://subnetkit.dev/port/445)
- [Port 464 (kpasswd)](https://subnetkit.dev/port/464)
- [Port 465 (SMTPS)](https://subnetkit.dev/port/465)
- [Port 500 (ISAKMP/IKE)](https://subnetkit.dev/port/500)
- [Port 502 (Modbus)](https://subnetkit.dev/port/502)
- [Port 512 (Rexec)](https://subnetkit.dev/port/512)
- [Port 513 (rlogin)](https://subnetkit.dev/port/513)
- [Port 514 (Syslog)](https://subnetkit.dev/port/514)
- [Port 515 (LPD)](https://subnetkit.dev/port/515)
- [Port 517 (Talk)](https://subnetkit.dev/port/517)
- [Port 518 (ntalk)](https://subnetkit.dev/port/518)
- [Port 520 (RIP)](https://subnetkit.dev/port/520)
- [Port 554 (RTSP)](https://subnetkit.dev/port/554)
- [Port 587 (Submission)](https://subnetkit.dev/port/587)
- [Port 631 (IPP)](https://subnetkit.dev/port/631)
- [Port 636 (LDAPS)](https://subnetkit.dev/port/636)
- [Port 646 (LDP)](https://subnetkit.dev/port/646)
- [Port 749 (kerberos-adm)](https://subnetkit.dev/port/749)
- [Port 853 (DNS over TLS)](https://subnetkit.dev/port/853)
- [Port 873 (rsync)](https://subnetkit.dev/port/873)
- [Port 989 (FTPS-DATA)](https://subnetkit.dev/port/989)
- [Port 990 (FTPS)](https://subnetkit.dev/port/990)
- [Port 993 (IMAPS)](https://subnetkit.dev/port/993)
- [Port 995 (POP3S)](https://subnetkit.dev/port/995)
- [Port 1080 (SOCKS)](https://subnetkit.dev/port/1080)
- [Port 1194 (OpenVPN)](https://subnetkit.dev/port/1194)
- [Port 1433 (MSSQL)](https://subnetkit.dev/port/1433)
- [Port 1434 (MSSQL Browser)](https://subnetkit.dev/port/1434)
- [Port 1512 (WINS)](https://subnetkit.dev/port/1512)
- [Port 1521 (Oracle)](https://subnetkit.dev/port/1521)
- [Port 1701 (L2TP)](https://subnetkit.dev/port/1701)
- [Port 1723 (PPTP)](https://subnetkit.dev/port/1723)
- [Port 1812 (RADIUS)](https://subnetkit.dev/port/1812)
- [Port 1813 (RADIUS accounting)](https://subnetkit.dev/port/1813)
- [Port 1883 (MQTT)](https://subnetkit.dev/port/1883)
- [Port 1900 (SSDP)](https://subnetkit.dev/port/1900)
- [Port 1935 (RTMP)](https://subnetkit.dev/port/1935)
- [Port 2000 (SCCP)](https://subnetkit.dev/port/2000)
- [Port 2049 (NFS)](https://subnetkit.dev/port/2049)
- [Port 2181 (ZooKeeper)](https://subnetkit.dev/port/2181)
- [Port 2222 (EtherNet/IP)](https://subnetkit.dev/port/2222)
- [Port 2375 (Docker)](https://subnetkit.dev/port/2375)
- [Port 2376 (Docker TLS)](https://subnetkit.dev/port/2376)
- [Port 2379 (etcd)](https://subnetkit.dev/port/2379)
- [Port 2380 (etcd peer)](https://subnetkit.dev/port/2380)
- [Port 2401 (CVS pserver)](https://subnetkit.dev/port/2401)
- [Port 3000 (Dev server)](https://subnetkit.dev/port/3000)
- [Port 3050 (Firebird)](https://subnetkit.dev/port/3050)
- [Port 3074 (Xbox Live)](https://subnetkit.dev/port/3074)
- [Port 3128 (Squid)](https://subnetkit.dev/port/3128)
- [Port 3268 (Global Catalog)](https://subnetkit.dev/port/3268)
- [Port 3269 (Global Catalog SSL)](https://subnetkit.dev/port/3269)
- [Port 3283 (Apple Remote Desktop)](https://subnetkit.dev/port/3283)
- [Port 3306 (MySQL)](https://subnetkit.dev/port/3306)
- [Port 3389 (RDP)](https://subnetkit.dev/port/3389)
- [Port 3478 (STUN/TURN)](https://subnetkit.dev/port/3478)
- [Port 3689 (DAAP)](https://subnetkit.dev/port/3689)
- [Port 3690 (Subversion)](https://subnetkit.dev/port/3690)
- [Port 4444 (krb524)](https://subnetkit.dev/port/4444)
- [Port 4500 (IPsec NAT-T)](https://subnetkit.dev/port/4500)
- [Port 5060 (SIP)](https://subnetkit.dev/port/5060)
- [Port 5061 (SIP-TLS)](https://subnetkit.dev/port/5061)
- [Port 5222 (XMPP)](https://subnetkit.dev/port/5222)
- [Port 5269 (XMPP server)](https://subnetkit.dev/port/5269)
- [Port 5349 (TURN-TLS)](https://subnetkit.dev/port/5349)
- [Port 5353 (mDNS)](https://subnetkit.dev/port/5353)
- [Port 5432 (PostgreSQL)](https://subnetkit.dev/port/5432)
- [Port 5672 (AMQP)](https://subnetkit.dev/port/5672)
- [Port 5683 (CoAP)](https://subnetkit.dev/port/5683)
- [Port 5900 (VNC)](https://subnetkit.dev/port/5900)
- [Port 5984 (CouchDB)](https://subnetkit.dev/port/5984)
- [Port 5985 (WinRM)](https://subnetkit.dev/port/5985)
- [Port 5986 (WinRM HTTPS)](https://subnetkit.dev/port/5986)
- [Port 6379 (Redis)](https://subnetkit.dev/port/6379)
- [Port 6443 (Kubernetes API)](https://subnetkit.dev/port/6443)
- [Port 6514 (Syslog-TLS)](https://subnetkit.dev/port/6514)
- [Port 6600 (MPD)](https://subnetkit.dev/port/6600)
- [Port 6667 (IRC (de facto))](https://subnetkit.dev/port/6667)
- [Port 6881 (BitTorrent)](https://subnetkit.dev/port/6881)
- [Port 8000 (HTTP-alt)](https://subnetkit.dev/port/8000)
- [Port 8008 (HTTP-alt)](https://subnetkit.dev/port/8008)
- [Port 8080 (HTTP-alt)](https://subnetkit.dev/port/8080)
- [Port 8081 (HTTP-alt)](https://subnetkit.dev/port/8081)
- [Port 8086 (InfluxDB)](https://subnetkit.dev/port/8086)
- [Port 8096 (Jellyfin)](https://subnetkit.dev/port/8096)
- [Port 8200 (Vault)](https://subnetkit.dev/port/8200)
- [Port 8384 (Syncthing)](https://subnetkit.dev/port/8384)
- [Port 8443 (HTTPS-alt)](https://subnetkit.dev/port/8443)
- [Port 8500 (Consul)](https://subnetkit.dev/port/8500)
- [Port 8883 (MQTTS)](https://subnetkit.dev/port/8883)
- [Port 9000 (Alt-9000)](https://subnetkit.dev/port/9000)
- [Port 9042 (Cassandra)](https://subnetkit.dev/port/9042)
- [Port 9090 (Prometheus)](https://subnetkit.dev/port/9090)
- [Port 9091 (Transmission)](https://subnetkit.dev/port/9091)
- [Port 9092 (Kafka)](https://subnetkit.dev/port/9092)
- [Port 9100 (JetDirect)](https://subnetkit.dev/port/9100)
- [Port 9200 (Elasticsearch)](https://subnetkit.dev/port/9200)
- [Port 9418 (Git)](https://subnetkit.dev/port/9418)
- [Port 10050 (Zabbix agent)](https://subnetkit.dev/port/10050)
- [Port 10051 (Zabbix server)](https://subnetkit.dev/port/10051)
- [Port 10250 (Kubelet)](https://subnetkit.dev/port/10250)
- [Port 11211 (Memcached)](https://subnetkit.dev/port/11211)
- [Port 19132 (Minecraft Bedrock)](https://subnetkit.dev/port/19132)
- [Port 20000 (DNP3)](https://subnetkit.dev/port/20000)
- [Port 25565 (Minecraft)](https://subnetkit.dev/port/25565)
- [Port 27015 (Source engine)](https://subnetkit.dev/port/27015)
- [Port 27017 (MongoDB)](https://subnetkit.dev/port/27017)
- [Port 32400 (Plex)](https://subnetkit.dev/port/32400)
- [Port 47808 (BACnet)](https://subnetkit.dev/port/47808)
- [Port 50000 (IBM Db2)](https://subnetkit.dev/port/50000)
- [Port 61616 (ActiveMQ)](https://subnetkit.dev/port/61616)

## Trust
- [About](https://subnetkit.dev/about)
- [Privacy policy](https://subnetkit.dev/privacy): calculator input runs in your browser and is never uploaded; describes cookies and how third-party ads work when enabled.
- [Terms of service](https://subnetkit.dev/terms)
- [Contact](https://subnetkit.dev/contact)
- [Changelog](https://subnetkit.dev/changelog)