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Modbus Float Converter
Convert IEEE 754 floating-point values between Modbus registers and verify byte and word order.
Calculator
Ungrouped decimal, scientific notation, NaN, Infinity, or -Infinity.
A is the most-significant byte of the canonical IEEE-754 bit pattern. Modbus does not define the order of a 32-bit float.
A Modbus register is 16 bits and transmits its high byte first. For a two-register value, use the device documentation to select the 32-bit order.
Float32 value: 123456
Conversion
Float32 value
123456
Normal
Modbus registers
0x47F1 · 0x2000
Unsigned decimal: 18417 · 8192 · Signed INT16: 18417 · 8192
Hex in selected order
0x47F12000
Transmitted bytes: 47 F1 20 00
Canonical IEEE-754 hex
0x47F12000
A B C D: 47 F1 20 00
Sign / exponent / mantissa
0 / 143 / 0x712000
sign: 0 · stored exponent: 143 · mantissa: 7413760
32-bit integer views of canonical bytes
1206984704 / 1206984704
UINT32 / INT32
All byte orders
| Order | Hex / Transmitted bytes | Register 1 | Register 2 |
|---|---|---|---|
| ABCD (selected) | 0x47F12000 | 0x47F1 | 0x2000 |
| BADC | 0xF1470020 | 0xF147 | 0x0020 |
| CDAB | 0x200047F1 | 0x2000 | 0x47F1 |
| DCBA | 0x0020F147 | 0x0020 | 0xF147 |
Formula and calculation method
An IEEE-754 float occupies 32 bits and therefore two consecutive 16-bit Modbus registers. Modbus does not define the ordering of those two registers for 32-bit values, so devices use different byte and word orders.
A B C D = IEEE-754 bytes from most to least significant
ABCD: registers AB / CD · BADC: BA / DC
CDAB: registers CD / AB · DCBA: DC / BA
Assumptions and limitations
- A–D always refer to the canonical IEEE-754 bit sequence, not the browser's native memory order.
- Registers may be entered as decimal values or with a 0x prefix. Their valid range is 0…65535.
- NaN, ±Infinity, −0, and subnormal values are valid IEEE-754 states and are identified explicitly.
- Confirm the correct order from the device manual or by using a known test value.
Technical sources
Formulas and conventions were checked against these primary and manufacturer references.