The Grid Method (What)

The grid method is a method for carrying and canceling units when doing paper and pencil calculations.

For example, the next image shows a calculation of power to drive a pump using the the product of torque and angular speed.

As shown, units are carried and canceled using the “railroad tracks” or grid.

Rewards of the Method

1. Save huge amounts of time once you get skilled at this.

2. Eliminate many mistakes.

3. Always works; the method is general.

4. Anyone can follow your work. Excellent documentation.

5. Keeps work organized.

6. Equips you to solve problems by reasoning with units.

The Grid Method (How To)

1. Write down your equation with units you know.

2. Multiply by 1.0—the multiplicative identity—over and over until you get the units you want in your answer.

As you do your work, draw railroad tracks and cancel out units.