Ideal Gas Law Calculator
Ideal gas law calculator (PV = nRT) — enter three of pressure, volume, moles and temperature, solve for the fourth in SI units. Curriculum-aligned.
Ideal Gas Law Calculator
Enter any three values and leave the fourth blank — the calculator solves for it. Temperature must be absolute (K); if you enter °C it is converted first.
- Curriculum
- English (global) — Cambridge International + IB
- Built against
- Cambridge IGCSE 0620/0625 + IB Diploma (2023–2025) — The Ideal Gas Law
- Unit system
- SI primary; US/imperial readout below
- First published
- 2 Jun 2026
- Last updated
- 2 Jun 2026
View authoritative scientific sources
- NIST SP 811 (2008), §3 — units & conversions
- BIPM SI Brochure, 9th edition (2019)
- CODATA 2018 — molar gas constant R
- Ideal gas law — Encyclopædia Britannica
⚠️ Educational use only — see full disclaimer
EDUCATIONAL USE DISCLAIMER
This calculator is provided for educational and reference purposes only. It is not a substitute for instruction from a qualified teacher, your prescribed textbook, or your school's official curriculum materials.
When preparing for examinations, always cross-check our calculations and notation against your current syllabus and your teacher's guidance. Syllabus conventions and accepted notation vary between curricula and may change between examination years.
If you believe any calculation, notation, or curriculum reference in this tool is inaccurate, please let us know via the feedback button. We review feedback promptly and update tools when verified corrections are needed.
RECATOOLS accepts no liability for academic, examination, professional, or research outcomes arising from use of this tool.
How to Use the Ideal Gas Law Calculator
Pick your curriculum
Use the curriculum pills above to match your syllabus (Cambridge/IB, 高考 or SPM). Terminology and the whole page follow your selection.
Enter three values
Type three of pressure, volume, moles and temperature — leave the one you want to find blank. Each field has a unit selector.
Read the result
The answer is in SI units — kPa, litres, mol, kelvin — with a dimmed atm and °C readout below.
Check against your syllabus
The Tool Information block shows exactly which syllabus this is built against. Spot something off? Use the feedback button.
The Ideal Gas Law, in Your Curriculum's Words
The Ideal Gas Law (PV = nRT)
Example: What volume does 1.0 mol of an ideal gas occupy at 273.15 K (0 °C) and 101.3 kPa (1 atm)?
Given: n = 1.0 mol, T = 273.15 K, P = 101 325 Pa; R = 8.314 J/(mol·K). Using V = nRT / P:
V = (1.0 × 8.314 × 273.15) / 101 325 ≈ 0.0224 m³ = 22.4 L
The ideal gas law combines Boyle's, Charles's and Avogadro's laws into a single equation of state: PV = nRT. Here P is pressure, V is volume, n is the number of moles, T is the absolute temperature, and R is the molar gas constant (8.314 J/(mol·K)). This calculator accepts the usual units for each quantity, converts them to SI, and then solves for whichever quantity you leave blank.
Temperature must be in kelvin because it appears as an absolute temperature in the equation; entering °C and forgetting to convert is a common mistake, so the calculator converts it for you. One mole of an ideal gas occupies 22.4 L at STP (0 °C, 1 atm). Pressure and temperature also show an atm and °C readout. All calculation happens in your browser — nothing is uploaded, and it works offline once loaded.
The ideal gas law captures three earlier gas laws in a single equation — which is why it is so powerful in chemistry.
10 Facts About Gas Laws
The ideal gas law is PV = nRT.
The molar gas constant R = 8.314 J/(mol·K).
It combines Boyle's, Charles's and Avogadro's laws.
1 mol of ideal gas occupies 22.4 L at STP.
Temperature must be in kelvin, not °C.
Boyle's law: at fixed T, PV is constant.
Charles's law: at fixed P, V/T is constant.
Real gases deviate at high pressure and low temperature.
STP is 0 °C and 1 atm (101.325 kPa).
This calculator runs in your browser — your working stays private.
Frequently Asked Questions
- PV = nRT — pressure times volume equals the number of moles times the gas constant times the absolute temperature. Rearranged, you can solve for any one of the four quantities. The calculator uses R = 8.314 J/(mol·K) and SI units.
- SI units: pascals (Pa) for pressure, cubic metres (m³) for volume, mol for moles, and kelvin (K) for temperature. You may enter kPa, atm, bar or mmHg for pressure, L or mL for volume, and °C for temperature; the tool converts everything to SI. Pressure and temperature also show an atm and °C readout.
- Because T in PV = nRT is an absolute temperature. The Celsius scale has an arbitrary zero (the freezing point of water), so using °C directly gives the wrong answer. The calculator converts °C to kelvin (add 273.15) for you.
- STP means standard temperature and pressure, usually 0 °C and 1 atm. At these conditions, one mole of any ideal gas occupies 22.4 litres — the molar volume that appears so often in chemistry problems.
- Yes. Enter three of the four quantities and leave one blank — the calculator rearranges PV = nRT and solves for the missing value, whether pressure, volume, moles or temperature.
- The chemistry — PV = nRT — is identical worldwide. What changes is the terminology; "pressure" is 压强 in Chinese. The calculated value is the same.
- The Tool Information block lists the exact syllabus for your selected curriculum (e.g. SPM Kimia 4541). It is a study aid, not a substitute for your official syllabus or teacher.
- No. Every calculation runs in your browser; nothing you type is uploaded. It works offline once the page has loaded.
- Completely free, no account or usage limit. It runs entirely in your browser and collects no data.
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