Discussion about Units of Measurement

Hi Everyone,

I, for one, am really excited about the Units of Measurement feature.
There are a number of units already available in the code:

I have already added the pressure unit “bar” to the UoM

My question to you all is:

What units would you like to see added to the list?





Thanks @hr3, Harry,
I have added bars in a pull request already, but what units would you find useful?

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Really, no one want to add units to the system?

Flow rates? Fuel Efficiency? pH?

Humidity? Not sure if that has a UoM technically, as it’s usually expressed as a percentage.
Checked, and yes there are ‘absolute’ humidty units. Conversion to RH% not possible without further information (temp).

Rotational speed? e.g. rpm. I have no use-case for that!

You are correct technically but that’s already in the units


Number:Dimensionless Humidity "Humidity [%d %]"

What about RAIN mm/hr?
And I’m using a custom absolut humidity in g/m³ that can be even espressed in g/kg (g of water on kg of air)

And as the other thread you would like two more units of power VA and VAR, correct?
ApparentPower VA
ReactivePower VAR


That would be a Speed quantity, Thanks

That would be a new Type of Density with the base unit as SI kg/m³

That would be a Dimensionless unit part per thousand (I plan to add this)

yes and what about the speed Mbit/s or MByte/s?

New unit type DataRate what should the base unit be? bit/s or byte/s

Here they say the standard is B/s. b/s is only used when buying broadband from providers.
Must be kept in mind that the conversion between b/s to B/s is 8/1 and MB/s to B/s is 1024/1

It’s the week-end.
Has anyone requests for units to be added to the Units of Measurements
I am thinking of our friends from the USA.

US gallons?


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Have a look at the Datapoint types in KNX’s Engineering Tool Software. That will give you a pretty comprehensive list of building control related units of measurement.

This list is a bit old but is a starting point!

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Perhaps Nautical miles (distance), Knots (speed). Someone must have OpenHAB on a boat …

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I need:
litre / second (l/s)
cubic meter / hour (m3/hour)

What about µS/cm?

The electric conductivity e.g. also for soil fertility measurement as is the case with the Miflora sensor.

So far, electric charge has only unit C, mAh is not SI unit, but it’s also common unit for charge.

@vzorglub would litres be something to add? I noticed it was missing from the list. The HP Printers deal in microlitres/millilitres for marking agent used…

AFAIK LITRE should be available in SmartHomeUnits. It is possible to modify them by a MetricPrefix like MICRO or MILLI (e.g. MetricPrefix.MILLI(SmartHomeUnits.LITRE)). Does that work for you @Cossey?