Steam tables calculator (IAPWS-IF97) and Rankine cycle efficiency with a T-s diagram

Look up water and steam properties from pressure and temperature, saturation by pressure or temperature, or from pressure with enthalpy, entropy or quality, using the IAPWS-IF97 industrial formulation. Then work out a simple or reheat Rankine power cycle: turbine and pump work, heat in, thermal efficiency, exit quality, steam rate and a temperature-entropy diagram.

Keep it one tap away for everyday use.

State
Properties
Cycle
T-s plot

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Water and steam properties

Pressure unit Find from Pressure p (MPa) Temperature T (°C)

Range: 0 to 800 °C and up to 100 MPa (1,000 bar). Enthalpy, entropy and internal energy are zero for liquid water at the triple point (0.01 °C), as in all steam tables. Quality is the fraction of the mass that is vapour.

Rankine cycle

Boiler pressure (MPa) Turbine inlet temperature (°C) Condenser pressure (MPa) Turbine efficiency (%) Pump efficiency (%) Net power (MW, for the flow rates)

Reheat: expand part way, heat again, then expand the rest

Turbine efficiency is the actual work as a share of the work of an ideal (isentropic) expansion; pump efficiency is the ideal pump work as a share of the actual. Use 100 % for both to get the ideal cycle. Pipe and heat losses are ignored. The example values are made up.

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What it does

This is a steam table you never have to interpolate in. It works out the properties of water and steam from the IAPWS-IF97 formulation, the international standard used by power plant and boiler engineers, and then uses them to analyse a Rankine cycle, the cycle behind coal, gas, nuclear, solar-thermal and geothermal steam power stations.

Properties. Choose what you know:

Pressure and temperature for compressed liquid, superheated steam or supercritical fluid.
Saturation at a pressure or at a temperature: the boiling point, and side by side the liquid and vapour volume, enthalpy, internal energy and entropy, plus the heat of evaporation.
Pressure and enthalpy, pressure and entropy or pressure and quality, which tell you whether a state is wet steam (and how wet) or superheated, as you need after a turbine or a throttle valve.

You get specific volume, density, enthalpy, internal energy, entropy, cp, cv and the speed of sound, the IF97 region used, and the superheat or subcooling.

Rankine cycle. Give the boiler pressure, turbine inlet temperature, condenser pressure and the turbine and pump efficiencies. The tool follows the water round: pump (1 to 2), boiler (2 to 3), turbine (3 to 4) and condenser (back to 1), with an optional reheat stage. It reports the net work, heat in and out, thermal efficiency, back work ratio, turbine exit quality, steam rate, the Carnot limit and the steam flow for a given power, with a T-s diagram and a table of states.

How to use it

Pick the pressure unit: kPa, bar or MPa (1 MPa = 10 bar = 1,000 kPa). Temperatures are in °C.
Choose what you know and type the values. The answer updates as you type.
For the cycle, set the efficiencies to 100 % to see the ideal cycle, then lower them to see what real machines lose.
Tick Reheat and give the reheat pressure and temperature to see how reheating dries the turbine exhaust.

Worked example

Superheated steam at 10 MPa and 500 °C: h = 3375.1 kJ/kg, s = 6.5993 kJ/kg·K, v = 0.032813 m³/kg. Water boils at 311.0 °C at this pressure, so the steam has 189 K of superheat.

Rankine cycle (made-up plant): boiler 10 MPa, turbine inlet 550 °C, condenser 10 kPa (0.01 MPa, boiling at 45.81 °C), turbine 85 %, pump 75 %. The turbine gives 1157.3 kJ/kg and the pump takes 13.43 kJ/kg, so the net work is 1143.9 kJ/kg from 3296.7 kJ/kg of heat: a thermal efficiency of 34.70 %, against a Carnot limit of 61.25 %. The exhaust has a quality of 0.9000 (10 % moisture). The steam rate is 3.147 kg/kWh, so a 100 MW plant needs 87.42 kg/s of steam. Add reheat at 2 MPa back to 550 °C and the efficiency rises to 36.98 % with nearly dry exhaust (quality 0.997).

Tips

The reference state is the IF97 one: liquid water at the triple point has zero internal energy and entropy, so values match printed steam tables.
Very close to the critical point (373.946 °C, 22.064 MPa) properties change fast and IF97 is least certain; treat the last digit with care there.
Region 5 (above 800 °C) is not included.

FAQ

Why IF97 and not IAPWS-95? IF97 is the industrial standard: fast, and within a fraction of a percent of the scientific IAPWS-95 formulation, which it was fitted to.

Is this good enough for design? It is for study and planning, not a substitute for professional judgement. The cycle ignores pressure drops, heat losses and feedwater heaters.

Where the numbers come from

IAPWS (2007), Revised Release on the IAPWS Industrial Formulation 1997 for the Thermodynamic Properties of Water and Steam (IAPWS-IF97), International Association for the Properties of Water and Steam, www.iapws.org. Equations and coefficients of regions 1, 2, 3 and 4 and the B23 boundary are used as published in the release, a public international standard formulation.
Rankine cycle analysis with isentropic efficiencies: standard engineering thermodynamics, for example Çengel and Boles, Thermodynamics: An Engineering Approach (method only).
Checked against the verification values printed in the IAPWS-IF97 release and against the Python iapws package (IAPWS97) at about 100 points and five cycles. The example cycle is made up.

Standard scientific values, such as constants, atomic weights and melting points, are facts found in every textbook; we name where ours were checked. If you are an author or publisher and want a value, a credit or a table changed or removed, tell us and we will act quickly.

Last updated 2026-11-09.