Calculate theoretical mass from moles and molar mass for common compounds, or find percent yield from actual and theoretical mass values.

For theoretical mass, enter product moles already determined from the balanced reaction and limiting reactant. Compound molar masses are approximate.

Theoretical Mass Formula

The following formula is used to calculate the Theoretical Mass. 

TM = n × mm
  • Where TM is the Theoretical Mass (g)
  • n is the theoretical number of moles of product, determined from the balanced reaction and limiting reactant 
  • mm is the molar mass of the product  (g/mol) 

To calculate the theoretical mass, multiply the theoretical product moles by the product molar mass. Choose Custom molar mass to use the example values below. Percent yield is actual product mass divided by theoretical product mass, multiplied by 100; compare masses in the same unit.

How to Calculate Theoretical Mass?

The following example problems outline how to calculate Theoretical Mass.

Example Problem #1:

  1. First, determine the total number of moles.
    • The total number of moles is given as 5.
  2. Next, determine the molar mass of the product  (g/mol).
    • The molar mass of the product  (g/mol) is provided as 70.
  3. Finally, calculate the Theoretical Mass using the equation above: 

TM = n * mm

The values given above are inserted into the equation below and the solution is calculated:

TM = 5 * 70 = 350 (g)

Example Problem #2: 

For this problem, the variables needed are provided below:

total number of moles = 4

molar mass of the product  (g/mol) = 76

This example problem is a test of your knowledge on the subject. Use the calculator above to check your answer. 

TM = n * mm = ?