Pressure
The hPa on a weather map and the bar in your tyres – 1 bar = 100 000 Pa exactly, standard atmospheric pressure is 1 013.25 hPa. Edit, print and share.
The pressure table links a weather map’s hectopascals to a tyre’s bar and the scientific pascal: 1 bar = 100 000 Pa exactly, and standard atmospheric pressure is 1 013.25 hPa. Made for the classroom and home.
| 1 bar | = | 100 000 Pa |
|---|---|---|
| 1 bar | = | 1 000 hPa |
| 1 bar | = | 100 kPa |
| 1 kPa | = | 1 000 Pa |
| 1 hPa | = | 100 Pa |
| 1 atm | = | 101 325 Pa |
| 1 atm | = | 1 013.25 hPa |
| 1 mmHg | = | 133.322387415 Pa |
How the table works
Every row is a unit conversion: a quantity and unit on the left, the same quantity expressed in another unit on the right. The table is live – drag the handle to reorder, click a row to change the quantity or units, remove rows with the cross and add your own at the bottom.
Everything you change lands in the page address. Copy the link and others open exactly your table – handy when the whole class needs the same sheet. Your changes are also kept in your browser until you reset them, but only there: to share or keep them permanently, the link is what counts.
Print puts the table on a single portrait A4 and Download PDF gives you the same sheet as a file. Print practice sheet gives the table with empty answer cells and name/date lines – the normal printout is the answer key.
The weather map and the tyre measure the same quantity
hPa on the weather map and bar in a tyre are both pressure – just different units for the same quantity. 1 bar = 100 000 Pa exactly, and standard atmospheric pressure at sea level is 1 013.25 hPa (= 101 325 Pa).
Good to know: blood pressure is still measured in mmHg (millimetres of mercury) – a historical holdover from when pressure was measured with a mercury column. 1 mmHg = 133.322387415 Pa exactly. A normal reading, 120/80, means 120 mmHg systolic and 80 mmHg diastolic. The US psi (pounds per square inch, about 6 894.76 Pa) is not in the table – its exact value needs too many decimals for the exact-value rule, the same reason the exact US fluid ounce is prose-only on the volume page.
Roughly how much pressure?
- Tyre pressure is roughly 2.5 bar.
- Standard atmospheric pressure is roughly 1 013 hPa.
- Blood pressure is measured in mmHg, for example 120/80.
Frequently asked questions
How many pascals are there in a bar?
1 bar = 100 000 Pa.
What does hPa mean on a weather map?
Hectopascal, 100 Pa. Standard atmospheric pressure is roughly 1 013 hPa.
Why is blood pressure measured in mmHg?
Historically, pressure was measured with a mercury column. 1 mmHg = 133.322387415 Pa exactly – the unit survives in medicine.
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