4-20mA scaling calculator
Convert the 4-20mA current from an analog transmitter into the engineering value it represents (0–100 %, 0–10 bar, −40…+80 °C, and so on). Set the sensor minimum and maximum, then read the scaled result — or work backwards from a process value to the loop current.
4-20mA signal scaling
Formula: Result = Min + (Max − Min) × ((I − 4) / 16). A 4-20mA loop maps linearly: 4 mA is the low end of span, 20 mA the high end.
Reverse mode — current from process value
Formula: I = 4 + 16 × (val − Min) / (Max − Min), using the Min / Max above. Values outside the Min–Max span show “--”.
The scaled value is what a PLC or controller sees from the analog module on this loop. For the parts that read, transmit or isolate that signal — PLC analog I/O modules, 4-20mA transmitters and signal isolators — browse AO Ctrl's industrial automation catalog:
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Frequently asked questions
How do I convert a 4-20mA loop current into an engineering value?
The calculator uses Result = Min + (Max − Min) × ((I − 4) / 16). Because 4 mA is the live-zero low end and 20 mA the high end, the usable span is 16 mA — with the default 0-100 scale, a 12 mA reading scales to 50.
What does 12 mA correspond to on a 4-20mA loop?
12 mA is exactly 50 % of span, since it is the midpoint between the 4 mA zero and the 20 mA full scale. The calculator uses 12 mA as a typical mid-scale default — substitute your own measured loop current.
How do I work out the loop current for a target process value?
Use the reverse formula I = 4 + 16 × (val − Min) / (Max − Min). Enter the process value you want and the calculator returns the current a transmitter must output — 4 mA at the low end, 20 mA at the high end.