Free tool · IPv4 & IPv6

Subnet calculator

Enter an address with its prefix length to get the network, host range, netmask and size of the subnet.

IPv4 or IPv6 in CIDR notation, e.g. 10.0.0.0/8 or 2001:db8::/48. Runs in your browser.

Common IPv4 subnets

CIDR	Netmask	Addresses	Usable hosts
/32	255.255.255.255	1	1
/30	255.255.255.252	4	2
/29	255.255.255.248	8	6
/28	255.255.255.240	16	14
/27	255.255.255.224	32	30
/26	255.255.255.192	64	62
/25	255.255.255.128	128	126
/24	255.255.255.0	256	254
/23	255.255.254.0	512	510
/22	255.255.252.0	1,024	1,022
/20	255.255.240.0	4,096	4,094
/16	255.255.0.0	65,536	65,534
/8	255.0.0.0	16,777,216	16,777,214

Frequently asked questions

How many hosts are in a /24?

A /24 has 256 addresses; 254 can be used for hosts because the network address and the broadcast address are reserved.

What is a wildcard mask?

The inverse of the netmask (0.0.0.255 for 255.255.255.0). Cisco ACLs and OSPF configurations use it.

How big is an IPv6 /64?

2^64 addresses (about 18 quintillion). /64 is the standard size of a single IPv6 network segment; providers usually assign a /48 or /56 to a customer.

IP geolocation API

Get this data in your app

ipbase returns location, ISP, ASN, time zone and security flags (VPN, proxy, Tor, data center) for any IPv4 or IPv6 address, up to 100 addresses per request.

Get a free API key Read the docs

150 free requests every month. No credit card required.

GET https://api.ipbase.com/v2/info?ip=1.1.1.1

{
  "data": {
    "ip": "1.1.1.1",
    "type": "v4",
    "connection": {
      "asn": 13335,
      "organization": "APNIC and Cloudflare DNS Resolver project",
      "isp": "Cloudflare, Inc",
      "range": "1.1.1.0/24"
    },
    "location": {
      "country": { "alpha2": "AU", "name": "Australia" },
      "zip": "4000"
    },
    "security": { "is_vpn": false, "is_tor": false, "threat_score": 0 }
  }
}

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