Avogadro's Law Calculator: V1 / n1 = V2 / n2

How the volume of a gas changes when the amount of gas changes.

Calculated from standard textbook formulas, with every step shown. The formulas are fixed, so the working does not need checking: what matters is the numbers you type in. Use these calculators only if you are competent to choose the inputs (loads, material strength, dimensions, supports) and check your units and assumptions. For learning and checking your own working: design and sign-off are for a qualified engineer. Drafting Central does not store the numbers you type.

How this calculator works

Choose which quantity you want to find.

Enter the other values in the units shown.

The calculator gives the answer with the formula, the substituted numbers, and the answer in other units.

Formulas used

  • \frac{V_1}{n_1} = \frac{V_2}{n_2}
  • V_2 = V_1\frac{n_2}{n_1}

Worked example

With the default numbers in the calculator above:

  1. The formula, arranged to find the final volume: final volume = (starting volume x final amount of gas) / (starting amount of gas)
  2. Put the values in (every value in its SI unit): final volume = (5 x 0.75) / (0.5)
  3. The answer: final volume: 7.5 L
  4. The same answer in other units: 0.0075 m3; 7500 mL

Change the numbers in the calculator to see the full working, every step, for your own case.

Common questions

What is Avogadro's law?

Equal volumes of gases at the same temperature and pressure hold the same number of molecules, so the volume is proportional to the moles.

How much does a mole of gas fill?

About 22.4 litres at 0 C and 1 atmosphere, or 24.5 litres at 25 C.

Does the type of gas matter?

Not for an ideal gas. Real gases follow the law closely at low pressure.

Related calculators

Got a question about this? Ask an engineering question and get a plain-language answer with references.

Further reading: Any physics or chemistry text (the gas laws).

Need a calculator we do not have?

Tell us what you would like to calculate. We read every request and build the most asked-for ones.

We store your request (and your email if you give it) to decide what to build. We do not store the numbers you type into calculators.

Embed this calculator on your own page

Copy this code into your page. The calculator runs inside the frame and links back to Drafting Central.

Need this drawn, designed or checked?

Drafting Central is a mechanical engineering and drafting business working with customers across Australia and around the world. A calculator gives you the numbers; we can turn them into drawings and designs.

Need help with a real project?

Talk to Drafting Central →

← All engineering calculators