Kilopascals to Millibar

Appliance Gas Pressures: kPa on One Data Plate, mbar on the Next

A gas fitter carries one manometer and meets two unit systems. Installation standards and appliance labels in Australia and New Zealand quote working pressure in kilopascals — 1.13 kPa at the meter for natural gas, 2.75 kPa for LPG. The same class of appliance sold in the UK and continental Europe states its inlet pressure in millibars, and imported burner instructions, regulator stampings and combustion-analyser printouts follow suit. Reading a test point means being fluent in both.

The factor: 1 kPa = 10 mbar exactly, because a kilopascal is 1 000 Pa and a millibar is 100 Pa. So an Australian metering pressure of 1.13 kPa is 11.3 mbar, and a European natural-gas appliance rated at 20 mbar is asking for 2 kPa.

Where These Small Numbers Come From

The regulator sets the level

Gas arrives at the property well above appliance pressure and a service or cylinder regulator drops it to the nominal figure printed on the appliance rating plate.

Only millibars above the room

These are gauge pressures a few thousandths of an atmosphere above ambient — 20 mbar is about 204 mm of water column, which is why the trade measured it with a U-tube for a century.

Working versus standing

A test point tells a different story with the appliance firing than with it shut off, and the difference between the two readings is where most installation faults show themselves.

Gas type changes everything

Butane, propane and natural gas each run at their own pressure and their own injector size, so a pressure that is correct for one is badly wrong for another.

Checking a Test-Point Reading in Both Units

The sequence below assumes the manometer is already on the inlet or burner test point and the appliance is at rate.

Enter what the gauge says

If the instrument reads kilopascals, type it on the left — 1.13, 2.75, 0.87 — and millibars appear alongside. Decimal commas are accepted and stray spaces are ignored, which helps when a figure is copied out of a manual.

Hold it against the rating plate

Compare the converted value with the nominal pressure the manufacturer prints for that gas. A burner asking 37 mbar and a supply delivering 2.8 kPa are not the same thing — that is 28 mbar, a butane level on a propane appliance.

Move the figure to the paperwork

The copy button on either field puts the number on the clipboard with no unit attached, which is what a commissioning record or a certificate field expects. Pressing Ctrl + C in the field has the same effect.

Turn it round for the European spec

Press the swap arrows (↔) and the page runs mbar → kPa instead, for the far more common case of a British or European document quoting millibars to someone working in kilopascals. That direction is simply a division by ten: 37 mbar is 3.7 kPa.

Conversion is arithmetic, not commissioning. Gas work is licensed work: pressure tests, purging, soundness checks and appliance adjustment must follow the standard and the manufacturer's instructions in force where the installation is.

Supply and Burner Pressures by Gas Type

Nominal figures that appear on rating plates, regulators and test-point specifications, written in both units. Actual acceptable ranges come from the appliance instructions and the local installation standard — these are the reference points those documents are built around.

Gas and context	kPa	mbar	Where it is quoted
Natural gas, appliance inlet	2.0 kPa	20 mbar	UK and much of continental Europe
Natural gas, metering pressure	1.13 kPa	11.3 mbar	Australian standard domestic installation
Natural gas, appliance operating	1.1 kPa	11 mbar	Australia and New Zealand
Butane, cylinder regulator	2.8 kPa	28 mbar	UK low-pressure butane fittings
Butane/propane combination regulator	3.0 kPa	30 mbar	Common European leisure and catering kit
Propane, low-pressure regulator	3.7 kPa	37 mbar	UK and European propane appliances
LPG, appliance supply	2.75 kPa	27.5 mbar	Australia and New Zealand
Natural gas burner, 3.5 in water column	0.87 kPa	8.7 mbar	North American manifold pressure
Propane burner, 11 in water column	2.74 kPa	27.4 mbar	North American manifold pressure

Two patterns stand out. LPG always sits above natural gas, because it carries far more energy per cubic metre and the appliance compensates with much smaller injectors. And every figure in the table fits inside four kilopascals — under four per cent of atmospheric pressure — which is why gas manometers are built with a narrow span and read in tenths.

What This Page Does on a Service Call

Both fields follow the gauge

Type into whichever box matches your instrument and the other keeps pace, so a working-pressure and a standing-pressure reading can be checked one after the other.

One press to read the import manual

The swap arrows reverse the pair for millibar-to-kilopascal work, which is the direction most imported appliance literature forces on you.

Water column is in the list too

Both unit menus are searchable and cover mmH₂O and inH₂O alongside all the other pressure units, so a U-tube figure or a North American manifold spec converts on the same screen.

Certificate-ready digits

Copy hands over the number by itself, and results carry up to eight decimals, so a reading like 1.13 kPa lands as 11.3 rather than something you have to retype.

Gas Pressure Questions From the Test Point

Why does the same appliance quote millibars in Europe and kilopascals in Australia?

Both units measure exactly the same thing and differ only by a factor of ten. The European gas trade inherited the millibar from meteorology and kept it because appliance pressures land on convenient whole numbers — 20, 28, 30, 37. Australian and New Zealand standards went with the SI-derived kilopascal instead, so the same pressures appear as 2.0, 2.8, 3.0 and 3.7.

What is the difference between inlet working pressure and burner pressure?

Inlet working pressure is measured at the appliance connection with the burner alight, and it tells you what the supply and pipework can deliver under load. Burner or manifold pressure is measured downstream of the appliance gas valve and tells you what the injectors actually see. A healthy inlet figure with a low burner figure points at the valve or its adjustment rather than the supply.

What does regulator lock-up pressure tell a fitter?

Lock-up is the standing pressure the regulator settles at once every appliance is off. It always sits a little above working pressure, and the manufacturer states how much. A lock-up that climbs well past the stated allowance means the regulator is not sealing, which can push the appliance above its rated inlet pressure — the sort of drift that only shows up when you compare the firing and shut-off readings.

Why do appliances run on only a few tens of millibars?

An atmospheric burner does not need pressure, it needs flow and the right air entrainment. A gentle push of two or three kilopascals through a correctly sized injector gives the gas rate and jet velocity the venturi is designed around. Raising the pressure would lift the flame off the ports and upset combustion long before it improved anything.

How do inches of water column relate to these millibar and kilopascal figures?

One inch of water column is 249.09 Pa, so it is very close to 2.5 mbar or 0.25 kPa. That makes the North American 3.5 in WC natural-gas manifold figure about 8.7 mbar, and the 11 in WC propane figure about 27.4 mbar. Pick inH₂O or mmH₂O in either dropdown and the page handles that step for you.