All calculatorsSTP Gas Volume Converter
Convert a gas volume between given conditions and standard conditions using the combined gas law. Choose To STP (V, T, P → VSTP) or From STP (VSTP → V at T, P). Supports common STP/NTP definitions and unit conversions.
Background
For an ideal gas with constant moles, the combined gas law gives V₂ = V₁ × (P₁/P₂) × (T₂/T₁). This tool uses that relation to convert volumes to or from standard conditions.
How to use this converter
To STP
- Enter V, T, P at initial conditions. Pick your STP/NTP definition.
- We compute Vstd = V × (P/Pstd) × (Tstd/T).
From STP
- Enter Vstd at your chosen standard conditions and the target T, P.
- We compute V = Vstd × (Pstd/P) × (T/Tstd).
Ideal gas assumption; moles are constant (no leaks/reactions). Always use absolute temperature (K) in equations.
Example Problems & Step-by-Step Solutions
Example 1 (To STP)
V=2.00 L, T=25.0 °C, P=0.980 atm; STP=1 atm, 273.15 K.
Vstd=2.00×(0.980/1.000)×(273.15/298.15)=1.80 L.
Example 2 (From STP)
Vstd=1.00 L at STP (1 atm, 273.15 K). Target: 25.0 °C, 1.000 atm.
V=1.00×(1.000/1.000)×(298.15/273.15)=1.09 L.
Frequently Asked Questions
Q: Which STP should I use?
Many courses define STP as 1 atm and 273.15 K. Some references use 1 bar and 273.15 K. NTP is 1 atm and 293.15 K.
Q: Do I need Kelvin for temperature?
Yes—the combined gas law uses absolute temperature (K). Enter °C if you like; we convert to K internally.
Q: Can I convert mL as well as L?
Yes—choose L or mL. We output both for convenience.
Q: What assumptions are made?
Ideal gas behavior and constant amount of gas (n). Non-ideal gases or large pressure ranges may require compressibility factors.
