Type a number into the Pressure box, pick its unit, and the converter gives it in every other unit at once: psi, bar, kilopascals, megapascals, and feet or metres of head. The large figure is the conversion most people want (bar to psi, or psi to bar), and the line under the list says how that pressure would rate as a household mains supply. The US units and Metric buttons only change the starting value. The quick reference table below lists common values both ways.
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How the conversion works
Every pressure unit is a fixed multiple of the pascal, so the converter turns your number into kilopascals and then into the unit you want. One bar is exactly 100 kPa. One psi, a pound-force on a square inch, is 6.894757 kPa. Divide one by the other and you get the factor worth memorising:
psi = bar × 14.5038
Going the other way, divide psi by 14.5038. Head works the same way: a column of water 1 foot tall presses down with 0.433 psi, so every 10 feet of height costs about 4.3 psi. In metric, 10 metres of head is almost exactly 1 bar. That is why a shower two floors up feels weaker than the kitchen tap on the same supply.
Worked example: 2.5 bar
The converter opens with 2.5 bar in the box. Multiply by 100 and you have 250 kPa. Divide 250 by 6.894757 and you get 36.26 psi, which is the large figure the tool shows. The list underneath gives the rest:
- 36.26 psi
- 250 kPa
- 0.25 MPa
- 83.64 feet of head
- 25.49 metres of head
The reading line puts this below 40 psi, the point where showers may start to feel weak, especially upstairs. Press US units and the box resets to 60 psi, which converts to 4.14 bar and sits at the top of the normal band.
What your reading means
The reading line sorts any pressure into four bands, worked out in psi:
| Pressure | Reading | What it tends to mean |
|---|---|---|
| Below 40 psi (2.76 bar) | Low | Showers may feel weak, especially upstairs |
| 40 to 60 psi (2.76 to 4.14 bar) | Normal | Comfortable for most homes |
| 60 to 80 psi (4.14 to 5.52 bar) | High | Workable, but harder on valves and appliance hoses |
| Above 80 psi (5.52 bar) | Too high | Most US plumbing codes call for a pressure reducing valve |
Two things change how you should read it. First, the bands follow US practice. In many parts of Europe a supply of 2 to 3 bar (29 to 44 psi) is ordinary and the taps, showers and boilers are made for it, so "low" here means low by US standards, not necessarily faulty.
Second, the number on a combi boiler's dial is not mains pressure. That gauge shows the sealed heating circuit, which normally sits around 1 to 1.5 bar (14.5 to 21.76 psi) when cold. Run it through the mains bands and it looks alarmingly low when it is perfectly healthy. If that dial keeps dropping, the guide to a combi boiler losing pressure covers the usual reasons.
To get a mains figure worth converting, screw a hose-thread gauge onto an outside faucet or the washing machine valve, open that valve, and read it with nothing else running. That is static pressure. Then open a tap elsewhere and watch the needle. A small dip is normal. A big drop as soon as one tap opens points to a restriction somewhere in the pipework, and the guide to low water pressure causes walks through how to find it.
Toolbox
- EasyWater pressure test gauge (hose thread)
A 0 to 200 psi gauge that screws onto an outside tap or washer connection to read your water pressure.
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Picked from specifications and published reviews, not tested by us.
Limits, and when to call a plumber
The converter does arithmetic and nothing else. It cannot tell whether your gauge is accurate, and it treats every number as gauge pressure, the reading above the surrounding air, which is what household gauges, boiler dials and tyre gauges show. Atmospheric pressure, about 14.7 psi (1.01 bar), is not added in.
Pressure also isn't the same as flow. Good pressure with a feeble trickle usually means a blockage or scale, and the flow rate calculator measures that side of the story with a bucket and a timer.
Get a plumber in when:
- static pressure is above 80 psi (5.52 bar); a reducing valve on the main supply is the usual answer, and fitting one is a plumber's job
- the pressure climbs well above its static reading after the water heater has been running, which points to a closed system with no working expansion tank
- pressure has dropped across the whole house with no works in the street, which can mean a leak on the supply pipe
- an existing reducing valve has drifted, hums or chatters
Rules on maximum pressure and reducing valves vary by state and country; a local plumber will know which apply.
Where the figures come from
The conversion factors are defined values rather than estimates. The bar is defined as 100,000 pascals, and the psi factor follows from the definitions of the pound and standard gravity. Feet and metres of head use the conventional density of water at 39 °F (4 °C). The 80 psi ceiling is the limit written into the main US model plumbing codes, above which they ask for a reducing valve. The 40 and 60 psi marks are widely used rules of thumb, not legal limits.
FAQ
How many psi is 2.5 bar?
2.5 bar is 36.26 psi, or 250 kPa. As a mains supply that counts as low by US standards, although many European homes run on it without any trouble.
What is 1 bar in psi?
1 bar is 14.50 psi (14.5038 to four decimal places). It is also close to atmospheric pressure at sea level, which is about 1.01 bar.
How do you convert psi to bar?
Divide the psi figure by 14.5038, or multiply it by 0.0689. So 35 psi is 2.41 bar, 50 psi is 3.45 bar and 60 psi is 4.14 bar.
What are 1.5, 2, 3 and 10 bar in psi?
1.5 bar is 21.76 psi, 2 bar is 29.01 psi, 3 bar is 43.51 psi and 10 bar is 145.04 psi. The 10 bar figure turns up on valves and fittings marked PN10, which means they are rated for a nominal pressure of 10 bar.