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.
Building this into an app? Use the IP lookup API and its API quickstart.
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 and time zone for any IPv4 or IPv6 address, up to 1,000 addresses per POST request. Security flags (VPN, proxy, Tor, data center) are on the Small plan and above.
Read the documentation150 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": null, "is_tor": null, "threat_score": null }
}
}Free IP tools
ASN lookup
Owner and prefixes of any AS number.
Bulk IP lookup
Up to 100 IPs at once, CSV export.
IP address converter
Decimal, hex, binary, IPv4↔IPv6.
IP address lookup
Location and owner of any IP.
IP range to CIDR converter
Ranges to CIDR blocks and back.
Reverse IP lookup
Domains hosted on any IPv4 address.
VPN and proxy checker
VPN, proxy and Tor flags of any IP.
What is my IP address?
Your public IP, location and provider.
What is my ISP?
Which internet provider you use.
Cloud & bot IP rangesOfficial lists of AWS, Googlebot, GPTBot and more.
Example lookups: 8.8.8.8 · 8.8.8.0/24 · AS15169 · example.com · all IPv4 ranges