Converts a linear 4–20 mA signal between current, percent of range and the transmitter's engineering value — for loop checks, commissioning or finding out why a value in the control system doesn't match. Free, no sign-up; the calculation runs only in your browser.
The range may be negative (−50 … 150) or reversed (100 … 0). LRV and URV must differ.
The value is outside the nominal 4–20 mA range. The calculation is extended linearly; what such a signal means (fault, saturation, transmitter setting) has to be checked in the device documentation.
| Current [mA] | Range [%] | Value |
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For DP flow measurement with a square-root scale and low-flow cut-off, use: Flow calculator 4–20 mA →
The calculator checks the conversion. If the signal in the control system still doesn't match, the cause is often wiring, calibration, transmitter settings or PLC scaling — that is loop check and troubleshooting work.
With a linear transmitter, the loop current corresponds to a position in the measuring range:
Percent of range = (I − 4) / 16 × 100. The live zero at 4 mA separates a zero reading from a broken loop.
The electrical signal is always 4–20 mA. The engineering range is what the signal represents — it is set in the transmitter and must match the scaling in the PLC or control system.
Example: a transmitter ranged 0–16 bar with a 4–20 mA signal. At 12 mA the value is 0 + (12 − 4) / 16 × 16 = 8 bar.
Relation: EU = LRV + (I − 4) / 16 × (URV − LRV), and back: I = 4 + (EU − LRV) / (URV − LRV) × 16.
The calculation is valid for a linear signal only. Don't use it as is for:
The calculation assumes a linear 4–20 mA signal. It does not evaluate the configuration of a specific transmitter, NAMUR fault states, a SIL function, calibration tolerance or the accuracy of the measuring chain.
For commissioning or troubleshooting, check the result against the documentation of the specific device.