Enter the volume in gallons, the density, and the molar mass into the calculator to determine the number of moles.

Gallons To Moles Calculator

Enter any 3 values to calculate the missing variable

Gallons to Moles Formula

The following formula is used to calculate the number of moles from a given volume in gallons, density, and molar mass.

n = \frac{V \cdot 3.78541 \cdot 1000 \cdot \rho}{M}

Variables:

  • n is the number of moles
  • V is the volume in US gallons
  • ρ is the density in grams per milliliter (g/mL)
  • M is the molar mass in grams per mole (g/mol)

To calculate the number of moles, multiply the volume in US gallons by 3.78541 to convert it to liters, then multiply by 1000 to convert liters to milliliters (mL). Multiply by the density (g/mL) to get the mass in grams, and finally divide by the molar mass (g/mol).

US Gallons to Moles Conversion Table (Water, ρ = 1.00 g/mL; M = 18.015 g/mol)
Gallons (US) Moles (mol)
1/1613.133
26.265
1/635.020
¼52.531
70.041
78.796
½105.061
131.326
140.081
¾157.592
183.857
1210.122
262.653
1⅓280.163
315.183
367.714
2420.244
525.305
3630.367
4840.489
*Assumes water (ρ = 1.00 g/mL) and molar mass M = 18.01528 g/mol. US customary: 1 US gallon = 3.78541 L, so 1 gal ≈ 210.122 mol.

What is Gallons to Moles Conversion?

The conversion from gallons to moles involves determining the number of moles of a substance in a given volume of liquid. This is particularly useful in chemistry and chemical engineering where the amount of substance needs to be known for reactions and formulations. The conversion takes into account the volume of the liquid, its density, and the molar mass of the substance.

How to Calculate Gallons to Moles?

The following steps outline how to calculate the number of moles from gallons.


  1. First, determine the volume in gallons (V).
  2. Next, determine the density of the liquid (ρ).
  3. Next, determine the molar mass of the substance (M).
  4. Finally, calculate the number of moles using the formula n = (V * 3.78541 * 1000 * ρ) / M.
  5. After inserting the values and calculating the result, check your answer with the calculator above.

Example Problem : 

Use the following variables as an example problem to test your knowledge.

Volume in gallons (V) = 2

Density (ρ) = 1 g/mL

Molar Mass (M) = 18 g/mol