Kp Calculator
Use this Kp calculator to translate between the gas-phase equilibrium constants Kp and Kc.
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Run the calculator.
What This Kp Calculator Helps You Do
This page focuses on the one Kp workflow people usually need: converting between Kp and Kc once temperature and Delta n are known. That keeps the page fast and avoids mixing it with the separate job of building the equilibrium expression itself.
The result text reminds you what sign of Delta n is doing, which is where many conversion mistakes happen.
How to Calculate Kp Calculator
- Choose the conversion direction: Use Kc to Kp mode when concentration equilibrium data are known, or switch modes to recover Kc from Kp.
- Enter temperature and Delta n: The temperature must be in Kelvin, and Delta n should include only gaseous species.
- Apply the gas-equilibrium relation: The calculator raises RT to the Delta n power and uses that factor to translate between Kc and Kp.
- Interpret the difference: When Delta n is zero, Kp and Kc are equal at any temperature in this relation.
Kp Calculator Formula
| Variable | Meaning | Unit |
|---|---|---|
| Kp | Equilibrium constant based on partial pressures | dimensionless |
| Kc | Equilibrium constant based on concentrations | dimensionless |
| R | Gas constant | 0.082057 L·atm/mol·K when used with this form |
| T | Absolute temperature | K |
| Delta n | Moles gas products minus moles gas reactants | count |
Use the worked examples below to check how the formula behaves with real values. If the result looks unexpected, verify the unit assumptions and the meaning of each variable before interpreting the answer.
Worked Examples
- Kc: 2.50
- T: 500 K
- Delta n: 1
Result: Kp is about 102.6.
When gaseous moles increase, the RT term raises Kp above Kc at this temperature.
- Kc: 5.00
- T: 700 K
- Delta n: 0
Result: Kp is 5.00.
No change in total gaseous mole count means Kp and Kc are identical.
- Kp: 1.20
- T: 400 K
- Delta n: -1
Result: Kc is about 39.0.
With fewer gaseous moles on the product side, Kc can exceed Kp markedly.
- Kp: 250
- T: 900 K
- Delta n: 2
Result: Kc is much smaller than Kp.
Large positive Delta n and high temperature amplify the RT factor strongly.
How to Interpret Your Results
| Range | Meaning | Action |
|---|---|---|
| Delta n = 0 | No Kp/Kc difference from the gas-term conversion. | Use either constant directly in this temperature relation. |
| Positive Delta n | Kp exceeds Kc by an RT factor power. | Expect stronger divergence at higher temperature. |
| Negative Delta n | Kc exceeds Kp. | Check the sign of Delta n carefully before interpreting the conversion. |
Frequently Asked Questions
References
Last reviewed: March 2026