Take as your baseline the weight of the bar without any plates added. Olympic-style bars are 45 pounds, while the bars connected to Smith machines usually only weigh 15 pounds. For barbells that are fixed like dumbbells, the weight will be listed on the end plate.
Add the plates onto the bar. Typically the plates will begin at 2 1/2 pounds, followed by plates weighing 5, 10, 25, 35 and 45 pounds.
Add the weight of the plates to the bar's weight to find your total.
Record the weight, repetitions and sets during your workout. Label the exercise that was performed as well.
Enter the amount of weight lifted and multiply it by the number of repetitions. If you performed that exercise and weight for multiple sets then you can multiply this total by the number of sets. Example: Barbell bicep curls: 55 pounds, 2 sets, 12 repetitions. You multiply 2 x 55 x 12 and get 1,320 pounds as your total weight for this exercise.
Add all the exercise totals together to get the total weight that you lifted for the entire workout.