What PhaseGauge calculates

The calculator, saturated steam tables, and superheated steam tables share one IAPWS-IF97 engine with the thermodynamic diagrams. Steam tables are available in SI and US customary units. Values come from equations rather than interpolation between table rows.

Choose from eight input pairs: P–T, P–h, P–s, h–s, T–h, T–s, P–x, and T–x. The engine supports compressed liquid, wet steam, superheated vapor, and supercritical water within its calculation limits. Ambiguous input pairs and excluded critical-point inputs return an explanation.

Results contain 18 property fields in four groups:

  • State (5): pressure, temperature, specific volume, density, and vapor quality.
  • Energy (3): specific internal energy, specific enthalpy, and specific entropy.
  • Response (5): isobaric and isochoric heat capacities, speed of sound, isobaric expansion coefficient, and isothermal compressibility.
  • Transport & electromagnetic (5): dynamic viscosity, thermal conductivity, liquid–vapor surface tension, static dielectric constant, and ionization constant (pKw).

Supplemental IAPWS correlations supply the transport and electromagnetic properties within their validity ranges. A dash marks a property that is undefined or outside its applicable range.

For wet steam, the result table shows the saturated liquid, saturated vapor, and mixture side by side. The hfg, sfg, and vfg differences are calculated before display rounding. For P–x or T–x inputs with x = 0 or x = 1, only the requested saturation endpoint is shown.

Use Plot on a result to view T–s or h–s diagrams; open the full diagram to switch to p–T. A valid state outside a diagram's displayed range is identified below the figure. Select Compare on a saved history entry to compare it with the current result. Deltas are current minus reference, calculated before display rounding.

Units and precision

Calculations and stored results use double-precision numbers in canonical units (MPa, K, m³/kg, kJ/kg, and kJ/(kg·K)). Unit conversion uses stored values before display formatting. Changing display units or precision does not round the stored result.

Results default to eight decimal places. Choose 2–10 decimal places or 4–8 significant figures; the initial significant-figure setting is 5. Direct inputs display the entered text; changing their units updates it.

Pressure inputs may be absolute or gauge. Barg and psig add a fixed standard atmosphere of 101.325 kPa. For a measured local atmospheric reference, supply the corresponding absolute pressure in an absolute unit.

Data in this browser

Ordinary calculations run locally and do not upload input values or results. Browser storage holds settings and up to 200 recent plus 100 pinned calculations. The app does not add inputs, results, or history to analytics events.

Opening a shared calculation link or a full diagram link sends its state parameters in the request URL to the hosting infrastructure. The privacy page covers storage, shared links, and analytics.

Clearing site data removes saved records; private browsing may make storage unavailable, and Safari may clear script-written data after inactivity. Export records you need to keep.

CSV exports property values in canonical SI units at the selected display precision for spreadsheet use. JSON preserves full stored values and versioned records for later import. Use Print for the current result.

Methodology and verification

The calculation engine is pinned to a specific version. Automated tests compare selected outputs with published IAPWS check values and independent NIST reference data. Read the methodology and verification for governing releases, verification coverage, acceptance limits, and calculation boundaries.