What is the Antoine Equation for water boiling point?

The Antoine Equation is an empirical vapor pressure equation of the form log10(P) = A - B/(T + C). Solving for saturation temperature yields T = B/(A - log10(P)) - C, where A, B, and C are empirical parameters that depend on the temperature range.

What are the physical limits for liquid water boiling calculations?

Calculations are bounded by the triple point (0.01°C at 0.00611 bar) and the critical point (374.15°C at 220.64 bar). Outside this envelope, liquid water cannot exist in standard thermodynamic equilibrium.

Water boiling point vs pressure

Q: How does pressure affect the boiling point of water?

The boiling point of water is directly dependent on pressure. Under vacuum or reduced pressure, water boils at temperatures lower than 100°C (212°F). Under high pressures (above atmospheric pressure), the boiling point of water increases significantly.

Boiling point of water at different pressures

Water boiling point at vacuum pressure

Water boiling point at higher pressure

How does pressure affect the boiling point of water ?

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1. Water boiling point at vacuum pressure
2. Water boiling point Interactive Calculator & Excel
3. Water boiling point in pressure higher than atmospheric

The boiling point of water at standard atmospheric pressure (101325 Pa or 1.01325 bar) is 100°C. However, the boiling point changes significantly with pressure. This page provides tables, mathematical formulas, and an interactive calculation app to know what is the boiling point of water at different pressures.

1. Water boiling point at vacuum pressure

What is the boiling point of water at low pressure ?

When water is heated under vacuum, its boiling point is lower than at atmospheric pressure. The boiling point at different levels of vacuum can be found in the data table and graphs below.

Table 1 : Boiling point of water at different pressures (vacuum)

Absolute pressure [mbar abs]	Vacuum [mbar g]	Water boiling point [°C]	Water boiling point [°F]
1013.3	0	100	212
846.6	167	96	205
700.6	313	90	194
666.6	347	89	192
473.4	540	80	176
311.5	702	70	158
266.6	747	67	152
199.1	814	60	140
133.3	880	52	125
123.3	890	50	122
73.48	940	40	104
42.33	971	30	86
33.86	979	27	80
30.48	983	24	76
27.09	986	22	72
23.71	990	21	69
20.32	993	18	64
16.93	996	15	59
13.55	1000	12	53
10.16	1003	7	45
6.1	1007	0	32
3.39	1009.82	-6	21
1.69	1011.51	-14	6
1.33	1011.85	-17	1
0.67	1012.53	-24	-12
0.4	1012.87	-29	-21
0.34	1012.87	-31	-24
0.17	1013.04	-37	-35
0.13	1013.21	-40	-40
0.07	1013.21	-46	-50
0.03	1013.17	-51	-60
0.017	1013.19	-57	-70
0.003	1013.2	-68	-90

Water boiling point as a function of pressure (vacuum)

Water boiling point as a function of pressure (vacuum 0-30 mbar)

2. Water boiling point Interactive Calculator & Excel

Use the professional calculator below to determine the precise saturation temperature (boiling point) or saturation pressure of water. The calculations utilize standard multi-range thermodynamic Antoine coefficients tailored for elevated precision.

⚠️ ENGINEERING NOTICE & EDUCATIONAL DISCLAIMER: This interactive calculator is provided exclusively for preliminary estimation and educational purposes. It is not intended for detailed design or equipment procurement without certified vendor rating. No warranty, expressed or implied, is provided, and no liability is assumed.

Water Saturation & Antoine Calculator

Unit System:

Calculation Mode

Input Pressure (Pa)

Input Temperature (°C)

Active Operating Unit

Calculated Thermodynamic States

Antoine Equation Formula Representation

The calculation is based on the Antoine empirical equation representing vapor pressure behavior of pure substances:

\[ \log_{10}(P_{\text{mmHg}}) = A - \frac{B}{T_{\text{°C}} + C} \]

Solving for Saturation Temperature (Boiling Point \(T\)):

\[ T_{\text{°C}} = \frac{B}{A - \log_{10}(P_{\text{mmHg}})} - C \]

Where:

\(P_{\text{mmHg}}\) is water's absolute vapor pressure in mmHg (\(1\text{ bar} = 750.062\text{ mmHg}\)).
\(T_{\text{°C}}\) is the resulting saturation temperature in Degrees Celsius.
Empirical coefficients for Water:
- For Low Pressures / Vacuum (\(0\text{ °C} \le T < 100\text{ °C}\)):
  \(A = 8.07131, \quad B = 1730.63, \quad C = 233.426\)
- For Elevated High Pressures (\(100\text{ °C} \le T \le 374\text{ °C}\)):
  \(A = 8.14019, \quad B = 1810.94, \quad C = 244.485\)

You can also download the companion Excel workbook to run these evaluations offline: Water Boiling point Excel calculator (click here)

Note: The mathematical model matches the Antoine regression constants. While highly robust for general industrial utility (valid from 0°C up to near critical water envelope), always consult certified steam tables (IAPWS-IF97) for boiler thermal rating or detailed steam distribution piping configuration.

💡 PLANT ENGINEERING RULES OF THUMB & CO-SENSING LIMITS

1. Critical Thermodynamic Constraints: Pure liquid water cannot exist above its critical point temperature of 374.15°C (705.47°F) and pressure of 220.64 bar abs (3200 psia). Beyond this point, water transforms into a supercritical fluid.
2. Vacuum Deaerator Design: Vacuum systems operate at lower temperatures to protect thermally sensitive active compounds or to strip dissolved gases. Ensure vapor lines are designed for high volumetric flow rates, as vapor specific volume scales exponentially under high vacuum.
3. Cavitation Margin: Liquid water must maintain a suction pressure safely above its saturation vapor pressure at operating temperature to prevent centrifugal pump cavitation. Maintain a minimum NPSH margin of 0.5 m (20 inches) or 10-20% above NPSHr.

3. Water boiling point in pressure higher than atmospheric

What is the boiling point of water at high pressure ?

When water is heated under positive pressure, its boiling point climbs significantly higher than 100°C. Standard pressure saturation data is detailed below:

Table 2 : Boiling point of water at different pressures (pressure above atmospheric)

Absolute Pressure [bara]	Absolute Pressure [psia]	Water boiling point [°C]	Water boiling point [°F]
1.013	14.7	100	212
1.034	15	101	213
1.103	16	102	216
1.172	17	104	219
1.241	18	106	222
1.31	19	107	225
1.379	20	109	228
1.517	22	112	233
1.655	24	114	238
1.793	26	117	242
1.931	28	119	246
2.068	30	121	250
2.206	32	123	254
2.344	34	125	258
2.482	36	127	261
2.62	38	129	264
2.758	40	131	267
2.896	42	132	270
3.034	44	134	273
3.172	46	135	276
3.309	48	137	279
3.447	50	138	281
3.585	52	140	284
3.723	54	141	286
3.861	56	142	288
3.999	58	144	291
4.137	60	145	293
4.275	62	146	295
4.413	64	147	297
4.551	66	148	299
4.688	68	149	301
4.826	70	151	303
4.964	72	152	305
5.102	74	153	307
5.24	76	154	309
5.378	78	155	310
5.516	80	156	312
5.654	82	157	314
5.792	84	158	316
5.929	86	158	317
6.067	88	159	319
6.205	90	160	320
6.343	92	161	322
6.481	94	162	323
6.619	96	163	325
6.757	98	164	326
6.895	100	164	328
7.239	105	166	331
7.584	110	168	335
7.929	115	170	338
8.274	120	172	341
10.34	150	181	359
12.07	175	189	372
13.79	200	194	382
15.51	225	200	392
17.24	250	205	401
18.96	275	210	410
20.68	300	214	417
22.41	325	218	425
24.13	350	222	432
25.86	375	226	438
27.58	400	229	445
29.3	425	233	451
31.03	450	236	456
32.75	475	239	462
34.47	500	242	467
36.2	525	245	472
37.92	550	247	477
39.64	575	250	482
41.37	600	252	486
43.09	625	255	491
44.82	650	257	495
46.54	675	260	499
48.26	700	262	503
49.99	725	264	507
51.71	750	266	511
53.43	775	268	515
55.16	800	270	518
56.88	825	272	522
58.61	850	274	525
60.33	875	276	529
62.05	900	278	532
65.5	950	281	539
68.95	1000	285	545
75.06	1089	290	555
84.64	1228	298	570
98.78	1433	310	590
114.6	1662	321	610
127.9	1854	329	625
147.3	2136	341	645
163.3	2369	349	660
186.8	2710	360	680
213.5	3096	371	700
222.4	3226	374	706

Water boiling point as a function of pressure

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