Calculating your pressure (p) is straightforward once you know the Ideal Gas Law formula and what each input means. This guide explains the method in plain language, walks through a manual calculation, and gives worked examples you can follow — then you can do it instantly with the Ideal Gas Law Calculator.
What is Ideal Gas Law?
The Ideal Gas Law calculation tells you your pressure (p) from a few simple inputs. The figure you are solving for here is the pressure (p).
The Ideal Gas Law formula
The core formula is:
Pressure (P) = Amount of gas (n) × 0.082057 × Temperature (T) ÷ Volume (V)Here is what each input means:
- Amount of gas (n) — a value measured in mol. Example: 1 mol.
- Temperature (T) — a value measured in K. Example: 273 K.
- Volume (V) — a value measured in L. Example: 22.4 L.
How to calculate it step by step
- Write down the amount of gas (n) (for example, 1 mol).
- Write down the temperature (t) (for example, 273 K).
- Write down the volume (v) (for example, 22.4 L).
- Apply the formula above to get your pressure (p).
- Double-check the result with the Ideal Gas Law Calculator.
Worked examples
Example 1
| Input / Output | Value |
|---|---|
| Amount of gas (n) | 1 mol |
| Temperature (T) | 273 K |
| Volume (V) | 22.4 L |
| Pressure (P) | 1.0001 |
With amount of gas (n) of 1 mol, temperature (t) of 273 K and volume (v) of 22.4 L, the pressure (p) works out to 1.0001.
Example 2
With amount of gas (n) of 2 mol, temperature (t) of 273 K and volume (v) of 22.4 L, the pressure (p) works out to 2.0001.
| Result | Value |
|---|---|
| Pressure (P) | 2.0001 |
Example 3
With amount of gas (n) of 5 mol, temperature (t) of 273 K and volume (v) of 22.4 L, the pressure (p) works out to 5.0003.
| Result | Value |
|---|---|
| Pressure (P) | 5.0003 |
Tips for an accurate result
- Keep your units consistent — mixing, say, months with years or grams with kilograms is the most common source of error.
- Round only at the very end. Rounding inputs early can shift the final answer noticeably.
- Re-run the numbers whenever an input changes, rather than estimating from an old result.
Prefer not to do the maths by hand? — the Ideal Gas Law Calculator does it instantly, for free, with the formula and a worked example built in.
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