4–20 mA Instrumentation Calculator

Use this free 4–20 mA calculator to convert an engineering value into loop current or convert measured loop current back into the corresponding process value for transmitter scaling, calibration, commissioning, and troubleshooting study.

For a linear transmitter, percent span equals (PV − LRV) ÷ (URV − LRV) × 100. Current then equals 4 mA + percent span × 16 mA. The reverse calculation converts measured current back into engineering units.

A 4 mA live zero represents the calibrated zero process value. A 0 mA reading therefore suggests loss of loop current or an open circuit rather than a normal zero process value.

• Engineering value → mA scaling.
• Measured mA → engineering value conversion.
• Percent-of-span calculation.
• Worked 0–100 kPa example: 75% span = 16 mA.
• Live-zero and loop-troubleshooting reminders.