Standard Temperature and Pressure (STP & SATP

Thermodynamics, Gas Physics & Standard Reference State Metrology

Standard temperature and pressure definitions establish universal thermodynamic baselines:

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• Ideal Gas Molar Volume Formula**:

V_m = R · T_stdP_std

Total Volume (V) = n × V_m, Standard Gas Density (ρ) = (M_w) / (V_m)

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• Combined Gas Law State Conversion**:

V_std = V_1 × ( (P_1) / (P_std) ) × ( T_stdT_1 )

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• The Four Major Standard Reference Baselines**:

• IUPAC Modern STP (Since 1982): 0^ (273.15 K), 100.00 kPa (1 bar) V_m = 22.7110 L/mol

• NIST / Classical STP (Pre-1982): 0^ (273.15 K), 101.325 kPa (1 atm) V_m = 22.4140 L/mol

• IUPAC SATP (Standard Ambient): 25^ (298.15 K), 100.00 kPa (1 bar) V_m = 24.7896 L/mol

• ISO 13443 Standard Metric: 15^ (288.15 K), 101.325 kPa (1 atm) V_m = 23.6443 L/mol

How to Use This Calculator

Enter your Standard Reference Definition Standard — choose from IUPAC Modern STP (0°C / 273.15 K, 100 kPa / 1 bar → V_m = 22.711 L/mol), NIST / Classical STP (0°C / 273.15 K, 101.325 kPa / 1 atm → V_m = 22.414 L/mol), IUPAC SATP (25°C / 298.15 K, 100 kPa / 1 bar → V_m = 24.790 L/mol), Amount of Gas (Moles - n) (e.g. 1.00 in mol), Gas Molar Mass (g/mol) (e.g. 28.013 in g/mol), Non-Standard Volume to Convert (Optional V₁) (e.g. 1.00 in L), Initial Pressure (P₁ in atm) (e.g. 1.00 in atm), Initial Temperature (T₁ in °C) (e.g. 20.0 in °C), and Gas & Thermodynamic Benchmark — choose from Custom Gas & Conditions, Nitrogen N₂ (1.0 mol at IUPAC STP: 0°C, 1 bar) → V = 22.711 L | Density = 1.233 g/L, Oxygen O₂ (1.0 mol at NIST STP: 0°C, 1 atm) → V = 22.414 L | Density = 1.428 g/L. Verify your units match the formula standard (SI vs imperial) before entering values.

The Formula

Total Gas Volume: V = n * V_m

Standard Gas Density: rho = Mw / V_m (g/L)

Combined Gas Law conversion: V_std = V1 (P1 / P_std) (T_std / T1)

Worked Example

A chemist measuring 1.00 L of gas in a 20°C lab at 1.00 atm applies the Combined Gas Law to convert it to IUPAC Modern STP, discovering its true standard volume is 0.944 L with a molar volume of 22.711 L/mol.

Understanding Your Result

Force in Newtons (N): 1 N = 1 kg·m/s². Reference values: 1 kg object at Earth's surface weighs 9.81 N, atmospheric pressure 101,325 Pa (N/m²). Pressure benchmarks: car tire 30–35 psi (207–241 kPa), blood pressure systolic 120 mmHg (16 kPa), deep sea at 3,000m depth ~300 atm (30 MPa). Torque = Force × moment arm length — doubling the wrench length doubles the torque for the same applied force. Always verify whether gauge or absolute pressure is required for the application.