Write down the length of the molecule and the length of the lateral axis, or diameter, of the molecule. For example, a hydrogen molecule has a length of 0.74 A and a diameter of 0.52 A.
Express the figures you wrote down in Step 1 as ratios. The first number will be the length of the molecule and the second number will be the length of the lateral axis or diameter. In the example, the ratio would look like this: 0.74:0.52
Divide the the first number in the ratio by the second number in the ratio. This figure is your axial ratio. In the example we would divide 0.74 by 0.52. The axial ratio of the hydrogen molecule would be 1.423.
Write down the magnitude of the major axis and the magnitude of the minor axis in the electric field vector. For example, a field has a major axis magnitude of 5 decibels and a minor axis magnitude of 3 decibels.
Express the figures you wrote down in Step 1 as a ratio. In the example, the ratio would look like this: 5:3.
Divide the first number in the ratio by the second number in the ratio. This figure is the axial ratio for your electric field vector. In the example, you would divide 5 by 3. Your axial ratio for this example would be 1.667.