Professional IPv4 Calculator and Subnetting Tool for Visual Studio Code
IPCalc Pro is a fast, lightweight IPv4 calculator and subnetting engine built natively into Visual Studio Code. No browser, no external tools — just open the panel and get instant results as you type.
Features
Real-time IPv4 Analysis
Network address, broadcast, host range, netmask, wildcard mask and usable host count — updated instantly on every keystroke
Binary representation for Address, Netmask, Wildcard, Network, HostMin, HostMax and Broadcast
IP class detection — Class A / B / C / D (Multicast) / E (Reserved) / Loopback / Reserved
Public vs Private classification with correct RFC ranges (10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16)
Input Validation
Strict octet validation — each octet must be 0–255, rejects leading zeros and non-numeric input
Visual feedback: input border turns green for valid input, red for invalid
Clear inline error messages for malformed IPs and out-of-range prefixes
VLSM Subnet Builder
Split any network into N optimally-sized segments
Uses binary subdivision — each split halves the largest available block
Adjustable segment count via stepper control (1–128)
FLSM Subnet Builder
Divide a network into equal fixed-size segments by specifying a target CIDR mask
Shows all subnets with their host ranges (up to 128 subnets)
Subnet Builder — per-row details
Netmask (dotted decimal) displayed on each subnet row, color-coded in red to match the Analysis panel
Broadcast address displayed on each subnet row, color-coded in blue to match the Analysis panel
Host range (HostMin – HostMax) displayed between netmask and broadcast
Copy to Clipboard
One-click copy button on every subnet row
Visual confirmation (checkmark feedback)
UI
Terminal-inspired dark theme (JetBrains Mono font)
Two-panel layout: Analysis on the left, Builder on the right
Activity Bar icon — click the IPCalc Pro icon in the left sidebar to open instantly, no Command Palette needed
Fully self-contained — no CDN dependencies for logic, no React, no Babel
Retains panel state when switching editor tabs
How to Use
Open the Command Palette (Ctrl+Shift+P / Cmd+Shift+P on macOS)
Type IPCalc Pro: Open Calculator and press Enter — or simply click the IPCalc Pro icon in the Activity Bar (left sidebar)
The panel opens — type any IP/CIDR in the input field (e.g. 192.168.1.0/24)
Analysis updates in real time — switch between VLSM and FLSM in the Builder panel
Examples
Input
Network
Broadcast
Usable Hosts
192.168.1.0/24
192.168.1.0
192.168.1.255
254
10.0.0.0/8
10.0.0.0
10.255.255.255
16,777,214
172.16.0.0/16
172.16.0.0
172.16.255.255
65,534
192.168.0.0/30
192.168.0.0
192.168.0.3
2
Requirements
Visual Studio Code 1.80.0 or higher
No additional dependencies
Extension Commands
Command
Description
IPCalc Pro: Open Calculator
Opens the main calculator panel
Known Limitations
IPv4 only — IPv6 is not currently supported
Requires internet connection for the JetBrains Mono font (loaded from Google Fonts CDN); the tool works fully without it, just with a fallback monospace font
