4–20 mA Scaling Calculator
Convert a 4–20 mA signal to pressure, temperature or any engineering value — and calculate the current for a required value.
How the 4–20 mA conversion works
A 4–20 mA transmitter maps its measurement range to a current loop. 4 mA represents the lower range value (LRV) and 20 mA represents the upper range value (URV). The relationship is linear.
Current to value: value = LRV + (mA − 4) / 16 × (URV − LRV)
Value to current: mA = 4 + (value − LRV) / (URV − LRV) × 16
When to use it
- Checking a pressure transmitter reading against a multimeter
- Converting a PLC analogue input into engineering units
- Setting up a transmitter range
- Estimating the current at a trip or alarm point
For a complete loop check, confirm the supply voltage, loop resistance and receiver input. See our pressure transmitter with LED display and Pt100 temperature transmitter.
FAQ
What is the 4–20 mA formula?
Value = LRV + (current − 4) / 16 × (URV − LRV). Current = 4 + (value − LRV) / (URV − LRV) × 16.
Why 4 mA and not 0 mA?
A 4 mA live zero lets the system distinguish a valid zero reading from a broken wire or failed transmitter.
Can I use this for pressure and temperature?
Yes — the math is the same for any 4–20 mA signal. Enter the LRV and URV in your engineering unit (bar, psi, °C, etc.).
What is a typical accuracy?
The transmitter accuracy is usually quoted as a percentage of full scale, e.g. 0.2% FS. The 4–20 mA conversion itself does not add error.