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4–20 mA Gas Calculator

Convert a gas transmitter’s 4–20 mA output to concentration, or calculate the expected loop current for a known gas reading.

Two-way conversionNon-zero measuring rangesOut-of-range signal warning

Configure the transmitter range

Convert either loop current to concentration or concentration to loop current.

Linear signal

Signal result

The standard measurement span is 4 to 20 mA.

Calculated concentration—
Loop current—
Percent of span—
Signal equation—
Normal measurement range

The signal is within the configured 4–20 mA measurement span.

Instrument-specific fault currents can differ. Check the transmitter manual before interpreting values below 4 mA or above 20 mA.
How the tool works

Apply a linear 4–20 mA scale

Four milliamps represents the configured lower range value and twenty milliamps represents the upper range value.

01

Enter the measuring range

Use the exact lower and upper values configured in the transmitter.

02

Choose the direction

Convert current to concentration or concentration to expected current.

03

Check fault conventions

Instrument-specific under-range and fault currents may differ.

Current to concentrationValue = low + (mA − 4) ÷ 16 × (high − low)
Concentration to currentmA = 4 + (value − low) ÷ (high − low) × 16
Percent span(Value − low) ÷ (high − low) × 100
Reference sources: Gas Nose gas detector resources. Always verify project-specific values against the applicable SDS, instrument manual, standard and site conditions.
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Frequently asked questions

4–20 mA Gas Calculator FAQ

Does 4 mA always equal zero gas?

No. It equals the configured lower range value, which can be non-zero.

What does 12 mA represent?

Twelve milliamps is 50% of the 4–20 mA span.

Can I interpret 3.5 mA as a gas concentration?

Only if the instrument manual defines that current as measurement data. Many transmitters use currents below 4 mA for fault or under-range states.

Does cable resistance change the conversion formula?

The linear scaling formula stays the same, but excessive loop resistance can prevent the transmitter from producing the intended current.

Need help applying the result?

Share the target gas, range, environment, equipment format and project quantity to review relevant gas sensors, modules or complete detectors.

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