Water - Boiling Points at Vacuum Pressure

Online calculator, figures and tables giving the boiling temperatures of water in varying vacuum, SI and Imperial units.

The boiling point of a substance is the temperature at which the vapor pressure of the liquid equals the pressure surrounding the liquid, and the liquid changes into a vapor. The boiling point of a liquid varies depending upon the surrounding pressure.

A liquid in a partial vacuum has a lower boiling point than when that liquid is at atmospheric pressure.

Online Water Boiling Point Calculator

The calculator below can be used to calculate the water boiling point at given, absolute pressures.
The output temperature is given as °C, °F, K and °R.

Note! ranges 0-1000 mbara, 0-14.7 psia, 0-760 mm Hg or 0-30 in Hg.

Below, figures and tables show the boiling point of water at varying vacuum .

See Water and Heavy Water for thermodynamic properties at standard condtions.
See also other properties of Water at varying temperature and pressure : Boiling points at high pressure, Density and specific weight, Dynamic and kinematic viscosity, Enthalpy and entropy, Heat of vaporization, Ionization Constant, pK_w, of normal and heavy water, Melting points at high pressure, Prandtl number, Properties at Gas-Liquid Equilibrium Conditions, Saturation pressure, Specific gravity, Specific heat (heat capacity), Specific volume, Thermal conductivity, Thermal diffusivity and Vapour pressure at gas-liquid equilibrium.

Boiling point as function of the pressure, given as "mm Hg below standard atmospheric pressure":
(= Vacuum of e.g. 100 mm Hg is the same as (760-100)=660 mm Hg absolute pressure)

The table shows the water boiling temperature at different vacuum pressure.
Vacuum is given as absolute pressure and pressure "below standard atmospheric pressure" (1 bara = 0 vacuum):

For full table with Vacuum and Water Boiling Point - rotate the screen!

Water - Boiling Points at Vacuum Pressure
Absolute pressure				Vacuum (below standard atmospheric pressure)			Water boiling point
(Microns) (μm Hg)	(in Hg)	(psia)	(mbara) *(100Pa)**	(in Hg)	(mmHg) (Torr)	(mbar) *(100Pa)**	(°C)	(°F)
760000	29.92	14.696	1013.3	0	0	0	100	212
635000	25.00	12.279	846.6	4.92	125.0	167	96	205
525526	20.69	10.162	700.6	9.23	234.4	313	90	194
500000	19.69	9.668	666.6	10.24	260.1	347	89	192
355092	13.98	6.866	473.4	15.94	404.9	540	80	176
233680	9.200	4.519	311.5	20.72	526.3	702	70	158
200000	7.874	3.867	266.6	22.05	560.1	747	67	152
149352	5.880	2.888	199.1	24.04	610.6	814	60	140
100000	3.937	1.934	133.3	25.98	659.9	880	52	125
92456	3.640	1.788	123.3	26.28	667.5	890	50	122
55118	2.170	1.066	73.48	27.75	704.9	940	40	104
31750	1.250	0.614	42.33	28.67	728.2	971	30	86
25400	1.000	0.491	33.86	28.92	734.6	979	27	80
22860	0.900	0.442	30.48	29.02	737.1	983	24	76
20320	0.800	0.393	27.09	29.12	739.6	986	22	72
17780	0.700	0.344	23.71	29.22	742.2	990	21	69
15240	0.600	0.295	20.32	29.32	744.7	993	18	64
12700	0.500	0.246	16.93	29.42	747.3	996	15	59
10160	0.400	0.196	13.55	29.52	749.8	1000	12	53
7620	0.300	0.147	10.16	29.62	752.3	1003	7	45
4572	0.180	0.088	6.10	29.74	755.4	1007	0	32
2540	0.100	0.049	3.39	29.82	757.4	1009.82	-6	21
1270	0.050	0.025	1.69	29.87	758.7	1011.51	-14	6
1000	0.039	0.019	1.33	29.88	759.0	1011.85	-17	1
500	0.020	0.0097	0.67	29.90	759.5	1012.53	-24	-12
300	0.012	0.0058	0.40	29.91	759.7	1012.87	-29	-21
254	0.010	0.0049	0.34	29.91	759.7	1012.87	-31	-24
127	0.005	0.0025	0.17	29.92	759.8	1013.04	-37	-35
100	0.0039	0.0019	0.13	29.92	760.0	1013.21	-40	-40
50	0.0020	0.0010	0.07	29.92	760.0	1013.21	-46	-50
25.4	0.0010	0.0005	0.03	29.919	759.9	1013.17	-51	-60
12.7	0.0005	0.00025	0.017	29.9195	760.0	1013.19	-57	-70
2.54	0.0001	0.00005	0.003	29.9199	760.0	1013.20	-68	-90

0% vacuum = 760 torr = 14.7 psia = 29.92 in mercury abs = 101.4 kPa abs
50% vacuum = 380 torr = 7.3 psia = 15 in mercury abs = 50.8 kPa abs
99.9% vacuum = 1 torr = 0.01934 psia = 0.03937 in mercury abs = 1.3 kPa abs