Vapor Pressure of Water at Different Temperatures
Vapor pressure of liquid water from 0 °C to 100 °C in torr, kPa, and atm. Needed whenever a gas is collected over water: subtract the water vapor pressure from the total pressure (Dalton's law, P_gas = P_total − P_H₂O) before applying the ideal gas law.
Vapor Pressure of Water, 0 to 100 °C
Water boils when its vapor pressure equals the external pressure; interpolate between rows as needed.
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| 0 | 4.6 | 0.613 | 0.00605 |
| 4 | 6.1 | 0.813 | 0.00803 |
| 10 | 9.2 | 1.227 | 0.0121 |
| 15 | 12.8 | 1.707 | 0.0168 |
| 20 | 17.5 | 2.333 | 0.0230 |
| 22 | 19.8 | 2.640 | 0.0261 |
| 25 | 23.8 | 3.173 | 0.0313 |
| 30 | 31.8 | 4.240 | 0.0418 |
| 35 | 42.2 | 5.626 | 0.0555 |
| 40 | 55.3 | 7.373 | 0.0728 |
| 45 | 71.9 | 9.586 | 0.0946 |
| 50 | 92.5 | 12.3 | 0.122 |
| 55 | 118.0 | 15.7 | 0.155 |
| 60 | 149.4 | 19.9 | 0.197 |
| 65 | 187.5 | 25.0 | 0.247 |
| 70 | 233.7 | 31.2 | 0.307 |
| 75 | 289.1 | 38.5 | 0.380 |
| 80 | 355.1 | 47.3 | 0.467 |
| 85 | 433.6 | 57.8 | 0.571 |
| 90 | 525.8 | 70.1 | 0.692 |
| 95 | 633.9 | 84.5 | 0.834 |
| 100 | 760.0 | 101.3 | 1 |
Important Notes
- Water boils when its vapor pressure equals the external pressure (exactly 760 torr, 1 atm, at 100 °C), which is why the table ends there.
- Collecting a gas over water: the trapped gas is saturated with water vapor, so P_dry gas = P_total − P_H₂O(T). Look up P_H₂O at the collection temperature here.
- Vapor pressure grows roughly exponentially with temperature (Clausius-Clapeyron); interpolate between rows for intermediate temperatures.
- This table is a general reference.
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