Free Modbus Tools
16 free online calculators, converters, and decoders for Modbus engineers and technicians. No signup required — use them directly in your browser.
RTUTCPConverterCalculatorDecoderReferenceGuideNetworking
RTU
Modbus CRC Calculator
Calculate CRC-16 checksum for Modbus RTU frames. Enter hex bytes and get the correct CRC instantly with full frame preview.
Open Tool
TCP
Modbus TCP Packet Builder
Build a valid Modbus TCP MBAP + PDU packet. Fill in Unit ID, Function Code, address, and data — get the hex frame instantly.
Open Tool
Address
Modbus Register Calculator
Convert between PLC-style addresses (40001) and zero-based register numbers. Identifies register type and function code to use.
Open Tool
Converter
Modbus Data Type Converter
Convert raw Modbus register values to INT16, UINT16, INT32, FLOAT32, and more. Supports Big Endian and Little Endian byte order.
Open Tool
Decoder
Modbus Hex Frame Decoder
Paste a raw Modbus RTU or TCP hex frame and decode every field with labels — Unit ID, FC, address, data, CRC validation.
Open Tool
RTU
Baud Rate Calculator
Calculate Modbus RTU bit timing, frame duration, and maximum poll rate for any baud rate and serial configuration.
Open Tool
Reference
Function Code Reference
Complete searchable reference for all Modbus function codes. Expand each FC for request/response format and register limits.
Open Tool
Decoder
Exception Code Decoder
Look up any Modbus exception code (01–0B) and get a plain English explanation, likely causes, and how to fix it.
Open Tool
Converter
Float to Register Converter
Convert IEEE 754 floating point numbers to two 16-bit Modbus registers and back. Shows all byte order configurations.
Open Tool
Converter
Byte Order / Endian Converter
Swap byte and word order for Modbus register values. Convert between Big Endian, Little Endian, Word Swap, and Byte Swap.
Open Tool
Calculator
Modbus Scaling Calculator
Convert raw Modbus register values to engineering units. Supports min/max scaling and gain + offset mode for sensors.
Open Tool
Converter
Binary / Hex / Decimal Converter
Convert numbers between Binary, Hexadecimal, Decimal, and Octal instantly. Supports 16-bit and 32-bit modes.
Open Tool
RTU
RS-485 Cable Length Calculator
Find the maximum RS-485 cable length for your baud rate. Includes termination resistor guidance and cable type recommendations.
Open Tool
Guide
Unit ID / Slave ID Finder
Step-by-step interactive guide to find the Modbus Unit ID of any device. Covers manuals, defaults, DIP switches, and brand tips.
Open Tool
Calculator
Modbus Poll Time Calculator
Calculate how long it takes to poll N Modbus registers at a given baud rate. Optimize your scan cycle for real-time control.
Open Tool
Scanner
Modbus Unit ID & Port Scanner
Scan a range of unit IDs (1–247) and ports to discover which Modbus TCP devices respond. Uses FC03 at address 0 — the same method as ModPackQT Master.
Open Tool
Networking
Network Detective
Auto-detect your local IP address, subnet mask, and default gateway in one click. Get copy-ready values for Windows, Mac, or Linux network settings.
Open Tool
ASCII
Modbus LRC Calculator
Calculate the Longitudinal Redundancy Check (LRC) for Modbus ASCII frames. Enter hex bytes and get the checksum and full ASCII frame instantly.
Open Tool
Ready to connect real Modbus devices?
ModPackQT is a free Modbus Master and Slave Simulator — connect to PLCs, energy meters, and VFDs directly in your browser.
Try ModPackQT Free →