4–20 mA Scaling Calculator
Convert between milliamps, PLC raw ADC counts, and engineering-unit values for any 4–20 mA transmitter or sensor range.
Input
Measured current, 4–20 mA
Results
Engineering value
—
% of span
—
%
Signal status
Formula used:
EU = EU_min + (mA − 4) ÷ 16 × (EU_max − EU_min)
EU = EU_min + (mA − 4) ÷ 16 × (EU_max − EU_min)
Input
Results
Signal current
—
mA
Voltage across 250 Ω (typical)
—
V
% of span
—
%
Formula used:
mA = 4 + (EU − EU_min) ÷ (EU_max − EU_min) × 16
mA = 4 + (EU − EU_min) ÷ (EU_max − EU_min) × 16
Input
e.g. 6208 for Allen-Bradley 1769-IF4 (0–20 mA, 16-bit)
Results
Engineering value
—
Equivalent mA
—
mA
% of span
—
%
Formula used:
% = (ADC − ADC_4mA) ÷ (ADC_20mA − ADC_4mA)
EU = EU_min + % × (EU_max − EU_min)
% = (ADC − ADC_4mA) ÷ (ADC_20mA − ADC_4mA)
EU = EU_min + % × (EU_max − EU_min)
Common ADC count references
| Module / platform | At 4 mA | At 20 mA | Resolution |
|---|---|---|---|
| Allen-Bradley 1769-IF4 (0–20 mA) | 6208 | 31208 | 16-bit signed |
| Allen-Bradley 1769-IF4 (4–20 mA) | 3277 | 16383 | 14-bit (0–16383) |
| Siemens S7-1200 AI (0–20 mA) | 5530 | 27648 | 16-bit signed |
| Siemens S7-1200 AI (4–20 mA) | 0 | 27648 | 16-bit signed |
| Generic 12-bit ADC (0–20 mA) | 819 | 4095 | 12-bit (0–4095) |
| Generic 16-bit ADC (0–20 mA) | 13107 | 65535 | 16-bit (0–65535) |
Always verify count ranges in your module's technical manual. Values above are from manufacturer documentation current at time of writing.
Disclaimer: This calculator is provided for preliminary estimation only. Always verify results against your specific module's technical manual and applicable standards before use in any engineering application. See Terms of Use.