First law
Delta U = Q - W
Thermodynamics calculator
First Law of Thermodynamics Calculator
Solve Delta U = Q - W using the sign convention that work done by the system is positive.
Calculator
Enter thermal values
Select units beside each input. Results update automatically.
Result
About this calculator
How it works
The first law relates heat transfer, work, and change in internal energy for a thermodynamic system.
Formulas
Formulas used
Worked example
Example calculation
Internal energy
Q = 500 kJ and W = 120 kJ gives Delta U = 380 kJ
Guide
How to use this calculator
- Enter the known temperature, pressure, energy, humidity, or material values.
- Select units beside each input where unit menus are shown.
- Use the highlighted result for screening and verify assumptions before design use.
Reference
What the results mean
Internal energy change
Energy stored in the system after heat and work interactions.
Sign convention
Positive work means work done by the system on surroundings.
Assumptions and limits
Before using the result
- Calculations use simplified ideal relations or common approximations for quick engineering checks.
- Real systems may require property tables, phase behavior, transient analysis, losses, and code or manufacturer data.
- Use verified data and qualified engineering judgement for final design or safety-critical work.
FAQ
First Law of Thermodynamics Calculator questions
Are these results suitable for final thermodynamic design?
Use these tools for education, screening, and early checks. Final work should use verified properties, standards, operating limits, and qualified engineering review.
Why can real thermal systems differ from these calculations?
Real systems include losses, non-ideal properties, transient behavior, two-phase effects, humidity assumptions, heat leaks, and measurement uncertainty.
Can I use different units?
Yes. Select units beside inputs where menus are shown. Values are converted internally before solving.
Related
Thermodynamics calculators
Dew Point Temperature Calculator
Estimate dew point from humidity conditions.
Enthalpy Calculator
Calculate enthalpy from internal energy and flow work.
Entropy Calculator
Calculate entropy changes.
Gibbs Free Energy Calculator
Evaluate spontaneity using Gibbs free energy.
Heat Transfer Calculator
Calculate heat transfer rates.