Subnet Calculator
Where does this address live — the network around it, the range it can hand out, and the two addresses it cannot.
Subnet Calculator
Results recalculate instantly on every keystroke. Nothing you type is transmitted.
What this result does not account for
- IPv4 dotted-quad only — IPv6 lives on its own page
- No supernetting advice — the CIDR page carves blocks
In short: 192.168.1.130 on a /26 lives in the network 192.168.1.128: 62 usable hosts from 192.168.1.129 to 192.168.1.190, with 192.168.1.191 reserved for broadcast. The mask 255.255.255.192 is just the /26 written in dots — and the wildcard 0.0.0.63 is its inverse, the form ACLs ask for. Every IPv4 address answers this question; this page reads the neighborhood for whatever you type.
Formula
network = ip AND mask · usable = 232−n − 2
The mask is a ruler drawn in bits: everything left of the line is the network's name, everything right of it is the address's seat inside that network. Two seats are never for sale — the all-zeros address names the network itself and the all-ones address is broadcast. The exceptions are worth their own lines: a /31 (RFC 3021) needs no broadcast on a point-to-point link, so both addresses are usable, and a /32 is a single host route with no neighborhood at all.
Worked Example
- Type the address in four octets.
- Set the prefix length from 0 to 32.
- Read the network, the host range and the ledger.
Defaults: 192.168.1.130/26 → network 192.168.1.128, 62 usable of 64. Drive the prefix to 30 and the same address reads a four-address point-to-point block with 2 usable hosts.
Strengths & Limits Of This Model
Where this engine is strong
- Wildcard printed beside the mask
- RFC 3021 and /32 read as real cases, not errors
Where it stops
- No VLSM plan across many blocks — one block at a time
Practical Use Cases
Interface config
netmask and gateway from one read
Firewall rules
the wildcard form ACLs ask for
Capacity checks
how many hosts the block can hold
Methodology & Editorial Standards
Computation runs in IEEE-754 double precision at full internal precision; rounding to two decimal places occurs strictly at the display layer, so no cumulative drift enters the result. All monetary outputs use accounting presentation — grouped thousands, two decimals, negatives in parentheses — so figures can be transcribed directly into a model or working paper. Division-by-zero and out-of-domain inputs return an em-dash rather than a misleading number.
This engine was reconciled against an independent reference implementation and hand-verified for the worked example above before release. Our full five-stage review process is published on the About Us page.
Disclaimer. This calculator is provided for informational and modelling purposes only and does not constitute financial, tax, legal, medical, or engineering advice. Verify all figures with a qualified professional before acting on them.
Subnet Calculator — 8 Expert FAQs
8 analyst-written answers to the questions practitioners actually ask — optimised for voice and answer-engine retrieval.
How do I calculate the number of hosts in a subnet?
Usable hosts = 2 to the power of (32 minus the prefix), minus 2. A /26 holds 2^6 = 64 addresses; subtract the network address and the broadcast address and 62 remain. The exceptions are /31, which carries 2 usable addresses under RFC 3021, and /32, which is one host route.
What do the network and broadcast addresses do?
The network address — every host bit zero — names the block itself and appears in routing tables; the broadcast address — every host bit one — reaches every host in the block at once. Neither can be assigned to a device, which is where the minus 2 comes from.
What is a wildcard mask?
The bitwise inverse of the subnet mask, written in dots. A /26 mask of 255.255.255.192 becomes the wildcard 0.0.0.63. Access-control lists and OSPF statements match on the wildcard form, which is why this page prints both.
Why does a /31 have no broadcast address?
RFC 3021 borrows the last /31 of a subnet for point-to-point links between exactly two routers. With only two addresses and exactly two speakers, broadcasting would be pointless — so both addresses are usable. It doubles the density of point-to-point addressing.
What does a /32 mean?
A single address with no neighborhood — a host route. Routing tables use /32 entries to pin one machine (a loopback, a BGP next-hop). There is no range to hand out and nothing to broadcast to.
Is this address public or private?
The page flags RFC 1918 private space (10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16), the loopback 127.0.0.0/8 and the link-local 169.254.0.0/16. Private space routes only inside your network; everything else needs NAT or a public assignment to reach the internet.
Where does the address sit inside its block?
The network card reports the offset — how many addresses into the range your address sits. 192.168.1.130 in its /26 sits 2 addresses in; the seat matters when you are deciding whether a device belongs to the block you think it does.
What about IPv6?
The IPv6 subnet page on this site reads the 128-bit twin: compressed and expanded notation, and the price of a prefix in /64 LANs. The reading habit transfers — prefix left of the slash, seat right of it — but the numbers stop being printable at 2 to the 64th.