---
id: iapws
version: "1.5.5"
license: gpl v3
license_treatment: copyleft
maintenance: active
---

# iapws — Python implementation of standards from The InternationalAssociation for the Properties of Water and Steam

License: copyleft · Maintenance: active · Downloads: 517.1K/mo

## What it is and what it does

iapws is a Python library that implements the full set of IAPWS (International Association for the Properties of Water and Steam) standards for calculating thermodynamic and transport properties. It covers water and steam (IF97, 95), ice (06), seawater (08), and heavy water (17). Given pressure, temperature, or quality state variables, it computes properties like enthalpy, entropy, density, and specific heat.

The library is designed for scientific and engineering applications that need accurate steam table lookups and thermodynamic calculations. It depends only on scipy for numerical operations and is available as a pure Python wheel. The package includes multiprocessing support for batch calculations and is actively maintained with support for current Python versions.

Use it for:

- Calculate steam properties for power plant cycle analysis given pressure and temperature inputs.
- Determine saturation conditions (enthalpy, entropy) for thermodynamic process modeling.
- Compute seawater thermodynamic properties for oceanographic or desalination engineering.
- Batch-process multiple thermodynamic states using the multiprocessing-enabled from_list method.
- Retrieve ice properties at specific temperature and pressure for cryogenic or glaciology applications.

## Worth the install?

AI-flagged interpretation of the facts above — verify before relying.

Calculates thermodynamic and transport properties of water, steam, ice, seawater, and heavy water according to IAPWS industrial standards (IF97, 95, 06, 08, 17).

Yes, if you need IAPWS standard thermodynamic calculations for water, steam, ice, or seawater. The package is actively maintained, has no known vulnerabilities, and installs with minimal friction. The GPLv3 copyleft license is a blocker only for proprietary closed-source projects; academic, research, and open-source work can use it freely.

## Install

pip install iapws
uv add iapws
poetry add iapws

## Installing iapws

Before you install: Low friction: pure Python wheel with a single runtime dependency on scipy. Active maintenance with a recent release (140 days ago) and ongoing repository activity.

License in practice: GPLv3 copyleft license: any derivative work or software that links this library must also be open-source under GPLv3. Suitable for academic and open-source projects; proprietary software integration requires careful licensing review.

Quickstart:

pip install iapws

from iapws import IAPWS97
sat_steam = IAPWS97(P=1, x=1)  # saturated steam at 1 bar
print(sat_steam.h)  # enthalpy in kJ/kg

Verify before relying:

- Whether the package handles edge cases and convergence issues mentioned in the TODO (two-phase region for IAPWS95 and D2O) without user workarounds.
- Performance characteristics for large-scale batch calculations beyond the multiprocessing example shown.

## Package facts

- License: gpl v3 (copyleft)
- Python support: supports_current
- Install friction: low
- Maintenance: active
- Downloads: 517.1K/month (top 15,000 on PyPI)
- Known vulnerabilities: none known

## Tags

steam table calculations, water thermodynamic properties, IAPWS standards implementation, steam enthalpy pressure temperature, seawater ice heavy water properties, thermodynamic state equations, scientific water properties library, thermodynamics, steam-tables, scientific-computing

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