4-20 mA Scaling Calculator (and 0-10 V)

Convert a 4-20 mA (or 0-10 V) analog signal to engineering units and back. Enter the range your transmitter is configured for, then type a current or a process value. Everything runs in your browser; nothing is sent to us.

1. Transmitter range
2. Signal → process value
3. Process value → signal
Scaling table
% of spanmApsi

The formula

Process value = Low + (mA − 4) ÷ 16 × (High − Low)

mA = 4 + (Process value − Low) ÷ (High − Low) × 16

Example: a 0-100 psi pressure transmitter reading 12 mA → 0 + (12 − 4) ÷ 16 × 100 = 50 psi. For 0-10 V signals, replace “mA − 4” with “V” and “16” with “10”.

Questions and answers

Why does the signal start at 4 mA and not 0?

The “live zero” lets the receiver tell a real 0 % reading (4 mA) from a broken wire or a dead transmitter (0 mA). It also leaves enough current to power 2-wire (loop-powered) transmitters.

What does a reading below 4 mA or above 20 mA mean?

The signal is outside the normal span. Under the NAMUR NE 43 convention used by many transmitters, 3.8-20.5 mA is the measuring range and values below 3.6 mA or above 21 mA signal a fault. Not every device follows NE 43, so check the manual of your transmitter.

How do I measure the loop current?

Put a multimeter in series with the loop on the mA range, or measure the voltage across a known resistor: 250 Ω turns 4-20 mA into 1-5 V.

Can I use 0-10 V instead of 4-20 mA?

Yes, if your PLC or controller has a voltage input. Current signals are less affected by long cable runs and electrical noise; voltage signals are simpler for short runs inside a panel.

Hardware with 4-20 mA signals in our catalog

Specifications below are taken from each product page; check the full listing before ordering.

Need several units? Send quantities and destination through our Wholesale & Bulk Orders page for a quote.