Kp and Kc Converter
Convert between the pressure equilibrium constant Kp and the concentration equilibrium constant Kc for gas-phase reactions.
Conversion direction
K
Converted equilibrium constant
- 1
R × T
0.08206 × 298 = 24.4539 L·atm/mol - 2
(RT)^Δn factor
24.4539^1 = 24.45388 - 3
Kp = Kc × (RT)^Δn
0.5 × 24.45388 = 12.226940
How does this calculator work?
Kp and Kc are linked by Kp = Kc·(RT)^Δn, with R = 0.08206 L·atm/mol·K, T in kelvin, and Δn the net change in moles of gas. Multiply Kc by (RT)^Δn to get Kp, or divide Kp by it to get Kc. If Δn = 0, Kp equals Kc.
Formula
How this is calculated
For a gas-phase reaction the pressure constant Kp and the concentration constant Kc are related by Kp = Kc·(RT)^Δn, where R is the ideal gas constant (0.08206 L·atm/mol·K when pressures are in atmospheres and concentrations in mol/L), T is the absolute temperature in kelvin, and Δn is the change in the number of moles of gas (moles of gaseous products minus moles of gaseous reactants).
Enter the constant you know (Kc or Kp), the temperature, and Δn. To go from Kc to Kp the calculator multiplies by the factor (RT)^Δn; to go from Kp to Kc it divides by the same factor. Δn is taken from the balanced equation counting only gas species — for example N2 + 3H2 ⇌ 2NH3 has Δn = 2 − 4 = −2.
When Δn = 0 the factor (RT)^0 = 1, so Kp = Kc and the two constants are numerically equal. The temperature must be positive (kelvin); a non-positive T or an invalid entry returns no result. Because R = 0.08206 uses atm and mol/L, Kp comes out in atmosphere units and Kc in mol/L units, each raised to the appropriate net power.
Frequently asked questions
Δn is the change in moles of gas for the reaction: the sum of stoichiometric coefficients of gaseous products minus that of gaseous reactants. Only gas-phase species are counted; solids and liquids are ignored.
That value of the gas constant is in L·atm/(mol·K), which matches pressures expressed in atmospheres and concentrations in mol/L. Use a temperature in kelvin so the units cancel correctly.
When Δn = 0, meaning the number of moles of gas does not change across the reaction. Then (RT)^0 = 1 and Kp = Kc.
Also known as
TG we-Calculate Editorial Team. (2026). Kp and Kc Converter [Online calculator]. TG we-Calculate. https://we-calculate.com/calculator/kp-kc-converter
TG we-Calculate Editorial Team. "Kp and Kc Converter." TG we-Calculate. 2026. https://we-calculate.com/calculator/kp-kc-converter.
TG we-Calculate Editorial Team, "Kp and Kc Converter," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/calculator/kp-kc-converter
@misc{wecalculate_kp_kc_converter, title = {Kp and Kc Converter}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/calculator/kp-kc-converter}}, year = {2026}, note = {TG we-Calculate} }
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