Saturated Steam Temperature Calculator and Pressure Guide

A saturated steam temperature calculator finds the temperature at which water and steam can coexist in equilibrium at a specified pressure. Enter absolute pressure in kilopascals (kPa); the calculator returns saturation temperature in degrees Celsius (°C), using a standard steam-property correlation.

Formula

The calculator uses an empirical saturation-pressure relationship rearranged to estimate temperature:

• t = 100 × [1730.63 / (233.426 − (log₁₀(p) − 0.006118) / (7.19621 − 0.000004p))]
• t is estimated saturation temperature in °C.
• p is absolute pressure in kPa. The constants in this correlation are fitted for pressure expressed in kPa; do not substitute bar, psi, or gauge pressure without conversion.

The second output converts Celsius to Fahrenheit: °F = (°C × 9/5) + 32. This correlation is a convenient approximation for liquid-water and steam saturation conditions over its useful range. For high-precision work, use a recognized steam-property formulation or property tables, especially near the critical point.

Worked Example

With the default pressure of 101.325 kPa absolute:

1. Calculate log₁₀(101.325), approximately 2.00572.
2. Calculate the denominator inside the fraction: 7.19621 − (0.000004 × 101.325) = 7.19580.
3. Calculate the temperature: 100 × [1730.63 / (233.426 − ((2.00572 − 0.006118) / 7.19580))] ≈ 100.00 °C.
4. Convert to Fahrenheit: 100.00 × 9/5 + 32 = 212.00 °F.

At standard atmospheric pressure, the result is therefore approximately 100.00 °C (212.00 °F), the familiar boiling point of water at that pressure.

What Saturated Steam Temperature Means

Saturation temperature is the temperature at which liquid water and water vapor can remain together in equilibrium at a given pressure. At this condition, adding heat can change liquid into vapor without immediately raising the temperature; that energy is associated with the phase change. Likewise, removing heat can condense vapor into liquid.

Pressure and saturation temperature are linked: increasing pressure raises the saturation temperature, while lowering pressure reduces it. This is why water boils at a lower temperature at high elevation, where atmospheric pressure is lower, and why pressurized water can remain liquid above 100 °C. The number is a property of water at equilibrium, not a guarantee that a pipe, vessel, or other system has reached equilibrium.

Absolute Pressure Versus Gauge Pressure

Steam-property relationships require absolute pressure, measured from a perfect vacuum. Many gauges instead report gauge pressure, measured above the surrounding atmosphere. Confusing the two can produce a substantially incorrect temperature.

• At sea-level standard atmospheric pressure, 0 kPa gauge is about 101.325 kPa absolute.
• To convert gauge pressure to absolute pressure, add the local atmospheric pressure: P_abs = P_gauge + P_atm.
• For example, 200 kPa gauge at standard atmospheric pressure is about 301.325 kPa absolute. Use 301.325 kPa in a saturation calculation, not 200 kPa.
• If a pressure instrument already reports absolute pressure, do not add atmospheric pressure again.

Atmospheric pressure varies with altitude and weather. For accurate conversion, use the local atmospheric pressure or the instrument’s stated reference rather than assuming standard atmosphere.

When to Use the Calculator—and Its Limits

Use a saturation-temperature calculation when you know the absolute pressure and need a quick estimate of the corresponding equilibrium temperature. It can help interpret steam tables, compare process readings, or check whether a reported temperature is broadly consistent with a pressure reading.

The result does not calculate how much steam is present, the heat required to produce it, steam quality (the fraction of a liquid-vapor mixture that is vapor), or the time required for heating. Those require additional information, such as mass, energy, flow, and the state of the material. A pressure-temperature match alone also does not establish that a system is safe or properly designed.

The equation is an empirical approximation rather than a complete, high-accuracy equation of state. Near water’s critical point, about 22.064 MPa absolute and 373.946 °C, property behavior becomes especially sensitive, so consult authoritative steam tables or a validated property package. The critical point marks the end of the distinct liquid-vapor saturation boundary; above it, there is no ordinary boiling or condensation transition.

Common Errors and Practical Checks

• Entering gauge pressure: Convert it to absolute pressure first. A low or even zero gauge reading does not mean zero absolute pressure.
• Mixing units: This calculator accepts kPa only. One bar is 100 kPa; 1 psi is approximately 6.89476 kPa. Convert before entering pressure.
• Assuming every steam line is saturated: Steam can be superheated, meaning hotter than saturation temperature at the same pressure. It can also be wet, with droplets mixed into vapor. In either case, pressure alone does not tell the actual temperature.
• Overinterpreting decimal places: Two displayed decimals are useful for reading the estimate, but they do not imply that the correlation or pressure measurement is accurate to 0.01 °C.

For a quick consistency check, compare measured pressure and temperature with a steam table at the same absolute pressure. A meaningful difference may indicate superheat, a two-phase mixture, instrument error, pressure loss between measurement points, or a system that is not at equilibrium.

Frequently Asked Questions

What is the saturation temperature of steam at atmospheric pressure?
At standard atmospheric pressure, 101.325 kPa absolute, water’s saturation temperature is about 100 °C (212 °F). Local boiling temperature varies with local atmospheric pressure.

How do I find steam temperature from pressure?
Use a steam table, a validated steam-property tool, or a suitable correlation. The pressure must be absolute, and the result is the saturation temperature—not necessarily the actual temperature of superheated or wet steam.

Is steam temperature the same as boiling-point temperature?
For saturated steam in equilibrium with liquid water at a specified pressure, yes: the saturation temperature is the boiling or condensation temperature at that pressure. Superheated steam is hotter.

Why is my pressure-temperature reading different from the calculator?
Check whether the pressure is gauge or absolute, whether pressure and temperature units are correct, and whether the steam is superheated or wet. Measurement location, instrument accuracy, and pressure drop can also matter.

Can steam be saturated below 100 °C?
Yes. At pressure below standard atmospheric pressure, the saturation temperature is below 100 °C. The boiling point is determined by pressure, not fixed at 100 °C in every location or system.

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in p | Absolute pressure | kPa | 101.325 | 0.6112 | 100000
out temp | Saturation temperature | °C | 100 * (1730.63 / (233.426 - (log10(p) - 0.006118) / (7.19621 - 0.000004 * p))) | 2
out ftemp | Saturation temperature | °F | temp * 9 / 5 + 32 | 2