Enter the washer outer diameter (in), the washer inner diameter (in), and the washer thickness (in) into the Flat Washer Weight Calculator. The calculator will evaluate the Flat Washer Weight. 

Flat Washer Weight Formula

The following formula is used to calculate the Flat Washer Weight. 

FWW = pi*(OD^2/4 - ID^2/4) * T * d


  • FWW is the Flat Washer Weight (lbs)
  • OD is the washer outer diameter (in) 
  • ID is the washer inner diameter (in) 
  • T is the washer thickness (in) 
  • d is the material density (lbs/in^3)

How to Calculate Flat Washer Weight?

The following two example problems outline the steps and information needed to calculate the Flat Washer Weight.

Example Problem #1

  1. First, determine the washer outer diameter (in).
    • The washer outer diameter (in) is calculated to be : 10.
  2. Next, determine the washer inner diameter (in).
    • The washer inner diameter (in) is measured to be: 5.
  3. Next, determine the washer thickness (in).
    • The washer thickness (in) is found to be: 2.
  4. Next, determine the density.
    • This is given as 1.25 lbs/in^3.
  5. Finally, calculate the Flat Washer Weight using the formula above: 

FWW = pi*(OD^2/4 – ID^2/4) * T * d

The values provided above are inserted into the equation below and computed.

FWW = pi*(10^2/4 – 5^2/4) * 2 * 1.25 = 147.462 (lbs)

Example Problem #2

The variables required for this problem are provided below:

washer outer diameter (in) = 30

washer inner diameter (in) = 20

washer thickness (in) = 5

Test your knowledge and check your answer with the calculator.

FWW = pI*(OD^2/4 – ID^2/4) * T * d = (lbs)