Free · No sign-up · Runs in your browser

Network engineering tools, free and instant.

The subnet math, conversions and lookups you reach for every day — fast, private, and free. Built by the team behind Elematron’s multi-vendor config generator and graded cert labs.

Open subnet calculator →Explore the platform
IP & Subnetting
/
IP Subnet Calculator
Network, broadcast, host range, mask & wildcard from any IPv4 + CIDR.
✂
Subnet Divider (VLSM)
Split a network into equal subnets and list every block.
∈
IP-in-Subnet & Overlap
Is an IP in a subnet? Do two subnets overlap? Answered instantly.
∗
Wildcard Mask Calculator
Convert subnet masks to wildcard masks for ACLs and OSPF.
#
IP / Binary / Hex Converter
Dotted-quad to binary, hexadecimal and 32-bit integer.
?
IP Address Type Checker
Public, private, loopback, APIPA, CGNAT or reserved?
Routing & Aggregation
Σ
Route Summarization
Aggregate a list of networks into the fewest summary routes.
⇄
IP Range ⇄ CIDR
An IP range to the minimal CIDR blocks, and CIDR back to a range.
C
OSPF Cost Calculator
Turn any interface bandwidth into its OSPF cost.
Troubleshooting
↕
MTU & MSS Calculator
Tunnel/encapsulation overhead to the right MSS clamp value.
B
Bandwidth & Transfer Time
How long a transfer takes at a given link speed.
Addressing
:
MAC Address Formatter
Reformat MAC addresses and read OUI, cast and admin bits.
6
IPv6 Expand & Compress
Expand to full form or compress IPv6 to its shortest notation.
Switching
↔
VLAN Range Expander
Expand 10-15,20 to a full list — or compress a list to ranges.
V
HSRP / VRRP Virtual MAC
Group or VRID to the well-known virtual MAC address.
Security
✱
Password & PSK Generator
Strong random passwords and pre-shared keys, generated locally.
Reference
≡
Subnet Cheat Sheet
The /0–/32 reference: mask, wildcard, hosts and block size.
→
Common Port Reference
Searchable list of well-known TCP/UDP ports and protocols.
AD
Administrative Distance
The default administrative distance for every routing source.
EF
DSCP & QoS Reference
DSCP names, decimal, binary and typical use for every marking.
DNS
DNS Record Types
What every DNS record type is for, at a glance.
IP
IP Protocol Numbers
Protocol field values: TCP 6, UDP 17, GRE 47, ESP 50.