Avogadro's Law Calculator

At fixed temperature and pressure, the volume of a gas is directly proportional to the number of moles present, written V1 / n1 = V2 / n2. Doubling the moles doubles the volume, which is why inflating a balloon adds both gas and size together.

Amounts n1 and n2 are in moles. Volumes can be in litres, millilitres, cubic metres, or anything else, as long as V1 and V2 use the same unit, because the law depends only on the ratio.

Yes. Avogadro's Law is valid only when temperature and pressure are held constant. If either changes between the two states, switch to the combined gas law or the ideal gas law, which include those variables.

Exactly three of V1, n1, V2, and n2. The Solve for dropdown blanks the fourth; if you also clear one of the others, the calculator reports that it needs exactly three inputs.

A real gas sample has a positive volume and a positive number of moles, so every entered value must be greater than zero. Zero or negative entries trigger an error instead of an unphysical answer.

No. It compares two states as a ratio and returns the missing volume or mole figure, not an absolute particle count. To turn moles into molecules, multiply by Avogadro's number, about 6.022 x 10^23.

The ideal gas law PV = nRT ties pressure, volume, moles, and temperature together at once. Avogadro's Law is the special slice of it where pressure and temperature are frozen, leaving just volume and moles in proportion.

Yes. For gases at the same temperature and pressure the mole ratio equals the volume ratio, so reacting-gas volumes follow the same proportion. This is the basis of the law of combining volumes.

No. The solver runs entirely in your browser with JavaScript, so the numbers you enter are never transmitted or stored elsewhere.