Modbus Register Calculator

Decode INT/DINT/REAL from Modbus registers, incl. byte and word swap.

READY

modbus_register_calculator.tool

READY

Registers (hex)

Byte / word order

Bytes: 41 C8 00 00

16-bit interpretation (register 0)

UINT16 / WORD16840

INT16 / INT16840

HEX0x41C8

BIN0100000111001000

32-bit interpretation (register 0 + 1)

UINT32 / UDINT1103626240

INT32 / DINT1103626240

REAL / FLOAT3225

HEX0x41C80000

// HOW IT WORKS

Modbus carries values in 16-bit registers. Larger data types (32-bit integers or IEEE 754 floats) span two consecutive registers. Enter the registers as hex – the tool shows the 16-bit interpretation of register 0 and the 32-bit value assembled from both registers.

Byte order

Reg0 = A B   Reg1 = C D
ABCD Big Endian · CDAB Word Swap · BADC Byte Swap · DCBA Little Endian

Example

0x41C8 0x0000 with ABCD → REAL/FLOAT32 = 25.0 (IEEE 754). A different order yields a different value – when unsure, try all four until the value looks plausible.

Notes

Each register is 16 bits; 32-bit values need two registers.
Differing byte/word order is the most common source of error for float values.
Function codes 0x03 (holding) / 0x04 (input) – see the reference table under /referenz.