Guide to water potential units

We measure water tension as a pressure signal according to the definition of the SI-unit system. This means a negative pressure like soil water tension is declared as a negative value.

pF:
hPa:
kPa:
MPa:
bar:
Psi:
Displayed decimal places:

The calculation needs JavaScript.

Tabular overview

	pF	hPa	kPa	MPa	bar	Psi	%rF
Wet	1	- 10	- 1	- 0,001	- 0,01	- 0,1450	99,9993
	2	- 100	- 10	- 0,01	- 0,1	- 1,4505	99,9926
FK field capacity	2,53	- 339	- 33.9	- 0,034	- 0,33	- 4.9145	99,9756
Standard tensiometer range	2,93	- 851	- 85.1	- 0,085	- 0,85	- 12.345
	3	- 1000	- 100	- 0,1	- 1	- 14.504	99,9261
	4	- 10000	- 1000	- 1	- 10	- 145.04	99,2638
PWP permanent wilting point	4,18	- 15136	- 1513	- 1,51	- 15	- 219.52	98,8977
	5	- 100000	- 10000	- 10	- 100	- 1450,4	92,8772
Air, dry, depending on humidity	6	- 1000000	- 100000	- 100	- 1000	- 14503	47,7632
Oven dry	7	- 10000000	- 1000000	- 1000	- 10000	- 145037	0,0618

Units definition

pF - is the base 10 logarithm of the water potential in cm
hPa - soil water pressure in [hPa] related to atmospheric pressure
kPa - soil water pressure in [kPa] related to atmospheric pressure
kPa - soil water pressure in [MPa] related to atmospheric pressure
bar - soil water pressure in [bar] related to atmospheric pressure
psi - soil water pressure in [psi] related to atmospheric pressure
%rF - is the relative humidity computed assuming an air temperature of 293 K