Electrical & Controls
4–20 mA scaling calculator
Convert a 4–20 mA signal to engineering units and back.
Calculating…
How it's calculated
PV = Low + (mA − 4) ÷ 16 × (High − Low)
mA = 4 + (PV − Low) ÷ (High − Low) × 16
4 mA represents the bottom of the range and 20 mA the top. Starting at 4 mA rather than 0 lets the receiving card tell a live zero from a broken wire.
- 12 mA is always 50% of span.
- NAMUR NE43: below 3.6 mA or above 21 mA indicates a fault.
- Across a 250 Ω resistor, 4–20 mA gives 1–5 V.