If you work in metallurgy, materials science, physical chemistry, or process engineering, you’ve almost certainly come across FactSage — one of the oldest and most established computational thermochemistry packages in the world. Released in 2001 and now in version FactSage 8.4 (July 2025), it remains a serious tool with serious heritage.
But FactSage isn’t the only player in this space. In this article, we provide an honest, in-depth review of FactSage, then compare it against its competitors and explain why for many users — especially those working with steels, superalloys, and industrial materials — Thermo-Calc 2026a is the smarter choice.
What Is FactSage and How Does It Work?
FactSage is an integrated computational thermodynamics system that uses the CALPHAD method (CALculation of PHAse Diagrams) to predict chemical equilibria, phase diagrams, and thermodynamic properties of multi-component, multi-phase systems.
In simple terms, FactSage lets you simulate how materials behave under varying conditions of temperature, pressure, and composition — without expensive, time-consuming experiments. For example, you can predict:
- Which phases form in a specific alloy at 1200°C
- How slag composition evolves in a melting furnace
- Under what conditions a chemical reaction reaches equilibrium
- The microstructure that will form during solidification
FactSage is the result of over 40 years of collaboration between two leading research centers: Thermfact/CRCT at École Polytechnique de Montréal (Canada) and GTT-Technologies in Aachen, Germany. Its roots go back to the F*A*C*T project (Facility for the Analysis of Chemical Thermodynamics), which began in 1976 as a joint venture between McGill University and the Université de Montréal.
Core FactSage Modules
FactSage’s strength is its modular architecture. Each module is designed for a specific type of calculation, and users can combine them as needed.
Equilib Module
Equilib is the beating heart of FactSage. It uses Gibbs Energy Minimization to compute complex chemical equilibria. The user defines reactants, selects possible products, sets final conditions (temperature, pressure, or other constraints), and Equilib calculates the equilibrium concentration of each chemical species.
Phase Diagram Module
This module generates binary, ternary, and multi-component phase diagrams. Recent versions implement automatic mapping of complete phase diagrams without requiring user-defined starting points — particularly valuable for higher-order systems.
Reaction Module
Calculates changes in extensive thermochemical properties (H, G, V, S, Cp, A) for a single species, mixture, or chemical reaction. Useful for analyzing simple reactions and understanding fundamental thermodynamics.
Predom Module
Generates predominance diagrams used in corrosion engineering and pyrometallurgical processes.
EpH (Pourbaix) Module
Plots Pourbaix diagrams showing equilibrium states in aqueous solutions as a function of pH and electrochemical potential E — essential for corrosion engineers and electrometallurgists.
Viscosity Module
Calculates the viscosity of molten oxide and glass phases. Particularly useful in glass technology and slag engineering.
OptiSage and CalphadOptimizer
Tools for optimizing G-function coefficients of compounds and Gibbs energy model parameters of solution phases. If you have new experimental data and want to build your own private database, these are your tools.
ChemApp for Python
A Python API that lets researchers integrate FactSage calculations into their Python scripts — increasingly valuable for automation and machine learning workflows in materials science.
What’s New in FactSage 8.4
The FactSage 8.4 release in July 2025 introduced several major features:
New Add-ons: FactFlow and FactProSim
These two new add-ons are offered free to users with active M&S (Maintenance & Service) contracts:
- FactFlow: A graphical environment for designing, analyzing, and optimizing process flowsheets without coding. Attractive for engineers who want to simulate entire metallurgical production lines.
- FactProSim: Local-equilibrium simulations using the EERZ (Effective Equilibrium Reaction Zone) approach with direct Microsoft Excel integration. Especially useful for steelmaking and refining processes.
Industrial Alloy Integration in Equilib
In version 8.4, you can directly define and select compositions of standard industrial alloys within Equilib — narrowing the gap between simulation and real-world materials.
Database Expansions
The FactPS, FToxid, GTOx, FSstel, FTlite, FTsalt, FScopp, FSlead, FTmisc, and SpMCBN databases have been significantly expanded in 8.4. Plus:
- FTionx: New database for ionic organic systems
- SGTE 2024: Updated alloy database
December 2025 Patch (Critical for All Users)
All users of FactSage 7.0 through 8.4 must apply the December 2025 patch to keep the software running after January 1, 2026. The patch fixes a date-handling bug in the .cdb (compound) database files.
FactSage Databases
FactSage’s databases are the core reason for its power. Built on CALPHAD assessments developed over decades:
Compound Databases
- FactPS: Most fundamental, for pure substances
- FTpulp: For pulp and paper industry
Solution Databases
- FToxid: FactSage’s most renowned strength — oxides, slags, and ceramics
- FSstel: Steels
- FTlite: Light alloys (Al, Mg, etc.)
- FTsalt: Molten and solid salts
- FScopp: Copper-based systems
- FSlead: Lead-based systems
- FTmisc: Miscellaneous including mattes and special alloys
- SpMCBN: Advanced ceramics (B, C, N)
- GTOx: Advanced GTT oxide database
- FTionx: Ionic organic systems (new in 8.4)
- FThall: For Hall-Héroult aluminum production
External databases like SGTE can also be added.
FactSage Industry Applications
FactSage is used across a wide range of industries:
Pyrometallurgy and Extractive Metallurgy
Simulating melting, refining, reduction, oxidation, and production of steel, copper, lead, zinc, aluminum and other base metals. Analysis of slag composition and behavior in various furnaces.
Hydrometallurgy
Aqueous solution equilibria, leaching processes, solvent extraction, and electrowinning.
Electrometallurgy
Electrolysis cell design, theoretical potential calculations, and electrolyte composition optimization.
Corrosion Engineering
Predicting metal corrosion in various environments using Pourbaix and Predominance diagrams.
Glass and Ceramics Industry
Viscosity calculations, thermal behavior, and oxide phase equilibria in glass formulations and advanced ceramics.
Combustion and Energy
Fuel combustion simulation, ash formation, and pollutant behavior in energy systems.
Geochemistry
Modeling geochemical processes at high temperature and pressure.
Environmental Studies
Pollutant fate analysis, waste system equilibria, and recycling processes.
FactSage 8.4 System Requirements
- OS: Microsoft Windows 10 or later
- CPU: Intel Core i7 2.8 GHz or equivalent AMD
- RAM: 16 GB or more
- Storage: 7200 RPM HDD or SSD
- License: Sentinel HASP Dongle or Cloud License
Important: FactSage runs only on Windows. macOS or Linux users must use a virtual machine.
FactSage Strengths
- Strong oxide and slag databases: FToxid is one of the most authoritative oxide databases in the world
- Long heritage and scientific credibility: Over 40 years of continuous development
- Diverse specialized modules: From Pourbaix to Viscosity
- Private database creation with OptiSage
- ChemApp for Python support for automation
- Excellent for extractive metallurgy and pyrometallurgical processes
FactSage Weaknesses and Limitations
Despite its strengths, FactSage has notable limitations:
- Dated user interface: Many users acknowledge the UI feels outdated compared to competitors
- Steep learning curve: While 2-3 days of training enables standard calculations, full mastery takes much longer
- Windows-only: No Linux or macOS support
- Steel and Ni-superalloy databases weaker than Thermo-Calc’s
- Limited advanced simulation modules: Such as diffusion modeling (which Thermo-Calc handles via DICTRA)
- Add-ons (FactFlow, FactProSim) limited in network installations
- FactSageEdu is highly restricted (e.g., Equilib and Phase Diagram cannot run simultaneously)
FactSageEdu: The Free Educational Version
A free version called FactSageEdu (currently FactSageEdu 8.4) is offered for students with these limitations:
- Standalone installation only (single computer)
- Equilib and Phase Diagram cannot run simultaneously
- No access to OptiSage, CalphadOptimizer, Results, Viscosity
- Cannot import ChemSage or TDB files
- No Macro Processing or ChemApp for Python access
- Internet connection required for validation
Suitable for teaching basic concepts, but not enough for serious research projects.
Best FactSage Alternatives in 2026
The computational thermochemistry market has grown substantially, and FactSage now faces serious competitors:
1. Thermo-Calc (Top Recommendation) ⭐
Thermo-Calc, developed by Thermo-Calc Software AB in Sweden, is FactSage’s most well-known competitor — and surpasses it in many key areas.
Why Thermo-Calc 2026a Is the Superior Choice
- Modern, professional UI: Users frequently praise Thermo-Calc’s interface as more user-friendly than FactSage
- Over 40 integrated databases in a unified platform — far more than FactSage
- Industry-leading steel and Ni-superalloy databases (TCFE, TCNI) used as the gold standard in aerospace, energy, and automotive industries
- Powerful standard calculators included with all licenses:
- Equilibrium Calculator
- Scheil Solidification Simulations
- Property Model Calculator
- General Model Library
- Material to Material Calculator
- Pourbaix Diagram Module
- Data Optimization Module (PARROT)
- Advanced add-on modules:
- TC-PRISMA: For precipitation simulation
- DICTRA: For thermodynamically-controlled diffusion simulation
- TC-Python: Mature Python API for automation
- Regular updates: Thermo-Calc 2026a delivers significant accuracy and performance improvements
Where Thermo-Calc Beats FactSage
| Criterion | Thermo-Calc 2026a | FactSage 8.4 |
|---|---|---|
| User Interface | Modern, intuitive | Dated, complex |
| Number of databases | 40+ | ~20 |
| Steel & Ni-superalloy | Excellent (TCFE, TCNI) | Average |
| Oxides & slags | Good | Excellent (FactSage strength) |
| Diffusion simulation | DICTRA (advanced) | Limited |
| Precipitation | TC-PRISMA (specialized) | Basic |
| Python API | TC-Python (mature) | ChemApp (developing) |
| Linux support | Yes | No |
| Learning curve | Moderate | Steep |
For full information, pricing, installation and download of Thermo-Calc 2026a, see our dedicated page:
🔗 Thermo-Calc 2026a Page on Docrack — Complete guide, new features, and download
2. Pandat
CompuTherm’s CALPHAD-focused software, particularly strong for aluminum and magnesium alloys. Good computational speed, but smaller database scope than Thermo-Calc and FactSage.
3. JMatPro
Focused on predicting mechanical, physical, and thermal properties of alloys. Popular in metallurgical and parts manufacturing industries — but more of an applied engineering tool than a fundamental thermodynamics platform.
4. MTDATA
Developed by NPL (UK). Mostly used in academic circles with significant UI limitations.
5. MatCalc
Focused on precipitation and kinetic simulation. Popular in academic research.
6. Open-Source Tools
- OpenCalphad: Open-source, free, but very limited UI
- PyCalphad: Python library for technical users
- Thermochimica: Open-source, developed by US national labs
These tools attract researchers and students but lack commercial-grade databases for industrial applications.
Which Software Should You Choose?
The choice depends on your specific work:
- Slag, glass, and oxide work: FactSage remains highly competitive
- Steel, superalloy, aluminum, and industrial alloy work: Thermo-Calc is the better choice
- Advanced diffusion and precipitation simulation: Thermo-Calc with DICTRA and TC-PRISMA
- Automation and machine learning: Thermo-Calc with TC-Python
- Limited educational projects: FactSageEdu is free
For most users — especially those in steel, automotive, aerospace, and industrial alloy industries — Thermo-Calc 2026a offers a better combination of power, database coverage, modern UI, and advanced tooling.
Frequently Asked Questions
Is FactSage free for students?
The educational version FactSageEdu 8.4 is free to download but heavily restricted. Full commercial licensing is required for serious research.
What’s the difference between FactSage and Thermo-Calc?
Both use the CALPHAD method, but Thermo-Calc offers a more modern UI, broader database coverage (especially for steel and Ni-superalloys), and more advanced add-on modules like DICTRA and TC-PRISMA. FactSage remains strong in slags, oxides, and glass systems.
Is FactSage 8.4 compatible with Windows 11?
Yes. FactSage 8.4 supports Windows 10 and later. Note that the December 2025 patch must be applied for the software to keep running in 2026.
FactSage or Thermo-Calc for steel research?
For steel, Thermo-Calc 2026a with its TCFE database — the global standard in steel research — is the superior choice. It’s used at major steelmakers worldwide including ArcelorMittal, POSCO, and SSAB.
Can I use FactSage and Thermo-Calc together?
Yes. Many advanced research centers use both tools complementarily — Thermo-Calc for alloys and superalloys, FactSage for complex slag and oxide systems. But if budget forces a single choice, Thermo-Calc offers broader coverage.
What are FactFlow and FactProSim?
These are new add-ons in FactSage 8.4: FactFlow for graphical process flowsheet design, and FactProSim for local-equilibrium simulations using the EERZ approach with Excel integration. Both work fully only in standalone (not network) installations.
Does FactSage support Linux?
No. FactSage runs only on Microsoft Windows. This is one of its limitations compared to Thermo-Calc, which also supports Linux.
What is CALPHAD?
CALPHAD stands for CALculation of PHAse Diagrams — a method for computing phase diagrams and thermodynamic properties of multi-component systems using mathematical models for phase Gibbs energies. Introduced in the 1970s by Larry Kaufman, it’s the foundation of all commercial thermochemistry software today.
How long does it take to learn FactSage?
According to the developer, 2-3 days of training is enough for a new user to perform standard calculations. But complete mastery of all modules and databases takes months of practical experience.
Conclusion
FactSage 8.4 is undoubtedly one of the most important computational thermochemistry platforms in the world, with a special place in pyrometallurgy, slags, oxides, and glass systems. New features like FactFlow and FactProSim enhance its appeal further.
That said, if your work focuses primarily on industrial alloys, steel, superalloys, diffusion and precipitation simulation, or Python automation, Thermo-Calc 2026a is the smarter choice. Its modern UI, broader database coverage, and powerful add-on ecosystem have made it the industry standard in many fields.
To learn more about Thermo-Calc 2026a — its new features, databases, and download/installation guide — click the link below:
Have questions or experiences with FactSage or Thermo-Calc? Share them in the comments.
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