CIDR notation expresses an IP address and its network prefix as a single string, e.g. 192.168.1.0/24. The number after the slash is the prefix length — how many bits belong to the network part.
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IP & Subnet Calculator
Calculate network addresses, host ranges, subnet masks, CIDR blocks, and wildcard masks — convert between prefix lengths, dotted-decimal, hex, and binary, entirely in your browser.
- ✔ CIDR / subnet calculator
- ✔ Subnet mask converter
- ✔ IP range → CIDR
- ✔ CIDR → IP range
- ✔ Bits-to-hosts table
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Network Planning Made Easy
Whether you're configuring a firewall rule, planning a VPC subnet on AWS or Azure, writing an ACL, or just trying to understand what address range a CIDR block covers — this tool does the arithmetic instantly. Enter an IP address with a prefix length or subnet mask and get the full breakdown: network address, broadcast, usable host range, wildcard mask, and a visual bit map showing which bits are the network part and which are the host part.
How It Works
1. Enter an IP + Prefix
Type 192.168.1.0/24 or an IP with a subnet mask.
2. Calculate
Get the full subnet breakdown instantly — no server needed.
3. Convert or Expand
Switch tabs to convert masks, compute ranges, or look up the bits-to-hosts table.
Enter a prefix length (e.g.
24), dotted-decimal mask
(e.g. 255.255.255.0), or hex mask (e.g. FFFFFF00) — the other
representations are calculated instantly.Enter a start and end IP address to get the minimal list of CIDR blocks that exactly covers that range.
Full reference for all IPv4 prefix lengths from /0 (entire internet) to /32 (single host).
| Prefix | Subnet Mask | Total IPs | Usable Hosts | Wildcard Mask |
|---|
Networking Reference
Common Private IP Ranges
| Name | CIDR | Range | Usable Hosts | Common Use |
|---|---|---|---|---|
| Class A Private | 10.0.0.0/8 | 10.0.0.0 – 10.255.255.255 | 16,777,214 | Large enterprise, cloud VPCs |
| Class B Private | 172.16.0.0/12 | 172.16.0.0 – 172.31.255.255 | 1,048,574 | Medium networks, Docker default |
| Class C Private | 192.168.0.0/16 | 192.168.0.0 – 192.168.255.255 | 65,534 | Home routers, small offices |
| Loopback | 127.0.0.0/8 | 127.0.0.1 – 127.255.255.254 | — | Localhost, testing |
| Link-Local | 169.254.0.0/16 | 169.254.0.1 – 169.254.255.254 | 65,024 | APIPA (no DHCP available) |
FAQsIP & Subnet Calculator
What is CIDR notation?
How many usable hosts does a /24 subnet have?
A /24 subnet has 256 total IPs, of which 254 are usable hosts. The first address is the network address and the last is the broadcast address.
What is a wildcard mask?
A wildcard mask is the inverse of a subnet mask — 0-bits mark the network portion and 1-bits mark the host portion. Wildcard masks are used in Cisco ACLs and OSPF configurations.