4-20mA Current Scaling Formula

This measurement to current converter tool will convert any linear measurement reading into the ideal current loop signal over a linear range of 4 to 20 milliamps, and display a 4-20mA conversion scale for the chosen measurement range.


This tool uses the following formula to calculate the current output signal over a 4-20mA scale from a specified measurement input reading and range:

Linear mA out = 4 + (16 x ((Rdg – Low Limit) / (High Limit – Low Limit)))


Measurement Unit

Add the measurement parameter value in the specified measurement unit you wish to convert.

Measurement Reading

Add the measurement parameter value you wish to convert in any units.

Lowest Measurement

Enter the lower limit for the measurement range to be converted. For example zero would be a typical value for most instrumentation but you can also add negative (-) or positive (+) values as well. Please enter the value in the same units as specified for all other input values.

Highest Measurement

Enter the upper limit for the measurement range to be converted, e.g. full scale or full range. This value can be negative (-) or positive (+). Please enter the value in the same units as specified for all other input values.

Current Loop Signal (4-20mA) – Answer

This is the ideal converted signal for the input measurement range specified, and represents the ideal output reading excluding all measurement and instrumentation errors. The calculated result is displayed in milliamps (mA) based on a linear 4 to 20 mA scaling.


Calculator precision

How precise is the calculation from measurement to linear 4-20mA output?

The linear 4 to 20 milliamp signal Answer is displayed to a precision of 9 significant figures.

Measurement types

What type of measurement can I convert?

Any measurement which is linearly proportional to the 4-20mA signal can be converted, such as pressure, temperature, force, load, weight, position, movement, speed, rpm, depth, level, etc…

Input & Output

Does it matter if the measurement is an input or a output?

No it does not matter if the measurement, the calculation is the same whether it is an input or an output.

Bidirectional measurements

Can I convert a bidirectional measurement?

Yes, you can enter the lowest measurement as a negative value by prefixing it with a minus (-) sign.

Compound ranges

Can I enter a compound range?

Yes, any negative range can be specified in the Lowest text box can be combine with any positive range specified in the Highest text box.

Elevated zero point

Is it possible to convert a measurement range where the lowest value is offset in positive direction from zero?

Yes, the lowest measurement point can start from any value above zero.

Measurement accuracy checking

Can this converter help to determine the accuracy of measurement instrument?

Yes, this converter will calculate the ideal 4-20mA signal so that you can compare it to an observed 4-20mA reading.

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