Subnetz berechnen
Subnetz-Details
| Netzwerkadresse | — |
|---|---|
| Broadcast | — |
| Nutbarer Bereich | — |
| Subnetzmaske | — |
| Wildcard | — |
| Adressen gesamt | — |
| Nutzbare Hosts | — |
| Adress-Effizienz | — |
| IP-Klasse | — |
| Maske (binär) | — |
💾 Subnetz steht. Jetzt den passenden Storage planen.
CIDR-Notation oder Host-Anzahl eingeben — alle Subnetz-Details auf einen Blick.
| Netzwerkadresse | — |
|---|---|
| Broadcast | — |
| Nutbarer Bereich | — |
| Subnetzmaske | — |
| Wildcard | — |
| Adressen gesamt | — |
| Nutzbare Hosts | — |
| Adress-Effizienz | — |
| IP-Klasse | — |
| Maske (binär) | — |
💾 Subnetz steht. Jetzt den passenden Storage planen.
A subnet calculator (also called CIDR calculator) determines all relevant network information from an IP address and subnet mask: network address, broadcast address, valid host range, and the number of available addresses.
In reverse mode, simply enter the number of hosts you need — the calculator automatically finds the optimal CIDR prefix and shows address efficiency. Perfect for VLAN planning.
Especially useful for network administrators when planning VLANs, troubleshooting IP address management, or preparing for certifications like CCNA or CompTIA Network+.
Every IPv4 address consists of 32 bits, represented as four decimal numbers (0–255). The CIDR prefix (/24) indicates how many bits form the network ID — the rest are host bits. A /24 network has 8 host bits = 2⁸ = 256 addresses, minus network address and broadcast = 254 usable hosts.
Instead of wasting a large /16 network (65,536 addresses), subnetting divides it into smaller units. Our Hosts→CIDR mode makes this easy: enter the number of hosts you need, and the calculator finds the optimal prefix — including an efficiency display showing how many addresses remain unused.
Two classic moments: you are planning VLANs for a new floor, or a DHCP scope should not grow bigger than necessary. That is exactly what this calculator is for — enter an IP and a prefix and you immediately see network address, broadcast, and usable range. No more mental arithmetic with powers of two, no more conversion errors between mask and prefix, and the question of whether a /24 is enough is answered in two seconds.
Type in an IP address, e.g. 192.168.10.5 — the exact host address does not matter, the calculator works with the network it belongs to.
Pick a prefix (/24, /26, …) or switch to reverse mode and enter the number of hosts you need.
Read off network address, broadcast, and usable range — including mask, wildcard, and efficiency.
You have a /24 (256 addresses) and four departments with about 50 devices each. Split it into four /26 subnets and you get 4 × 62 usable addresses — 248 of 256 in total. That is plenty and stays tidy: Sales .0/26, Development .64/26, IT .128/26, Administration .192/26. What remains are the network and broadcast addresses of each subnet — you need them for documentation just as much as for firewall rules.
A subnet mask comes in two notations: as a decimal mask (255.255.255.0) and as a CIDR prefix (/24). Both are identical — the prefix simply counts the set bits from the left. 255.255.255.0 is 24 set bits, hence /24. The calculator shows you both forms, so you never have to convert — but once you understand it, you read unfamiliar network configs much faster.
Because two addresses per network are reserved: the network address (all host bits are 0) and the broadcast address (all host bits are 1). Of the 256 addresses in a /24, 254 remain for real devices. A /30 (4 addresses) leaves only 2 usable — which is why /30s are typically used for point-to-point links.
A /32 is a single address with no network part — there is neither a network nor a broadcast address. Typical uses: loopback interfaces on routers (e.g. 10.0.0.1/32) or single-host routes in firewall rules.
VLSM (Variable Length Subnet Mask) means using different masks within the same network — the big department gets a /24, the small one a /28. No addresses are wasted. Classic subnetting with a uniform mask, on the other hand, left many addresses unused.
Private addresses per RFC 1918 (10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16) are not directly reachable from the internet. But that is not a firewall, it is simply address allocation: without NAT nothing from the local network reaches the internet either, and from outside you must actively open access — for example via port forwarding.
Solid background knowledge: RFC 1918 (private address ranges) and RFC 4632 (CIDR). Explained in depth in the blog article IPv4 Subnetting in 15 Minutes. Convert numbers into other formats with the Number Converter.
💾 Subnet configured? Now plan your storage with the RAID calculator.