Setting a budget for your investing expenses helps you plan for your costs. However, rarely do your budgeted amounts ever match up precisely with the actual costs. When measuring the deviation from the budgeted amount to the actual amount, you can measure the change as a percentage relative to the budgeted amount. This gives you a context for the significance of the difference. For example, if you go over budget by $1,000, and your budget is $500, that's a very significant change. However, if you budgeted $50,000, the difference is far less significant.

Subtract the budgeted amount from the actual amount to find the increase or decrease from the budgeted amount. For example, if you budgeted $1,200 for broker fees and you spent $1,340, subtract $1,200 from $1,340 to find you went over budget by $140.

Divide the amount by which the actual differed from the budget to find the rate of change. In this example, divide $140 by $1,200 to get 0.1167.

Multiply the rate by 100 to find the percentage change from the budget to the actual. Completing this example, multiply 0.1167 by 100 to find you went over budget by 11.67 percent.

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