How to Calculate a Monthly Budget

Write down your expenditures for a week. You can either do this by carrying around a small notebook and jotting down a note each time you spend money (even on the smallest purchases), or by holding onto all receipts and logging them at the end of the day. At the end of the week, divide your purchases up into categories to gain a better understanding of where your money is going. Your categories will likely include groceries, eating out, entertainment and transportation, and may include categories specific to your lifestyle, like classes or sporting activities.

Create a projection for your monthly spending based on your week-long journal. Add your recurring monthly payments, such as credit card, cell phone and loan bills, to the total. The grand total is the amount of money you're spending each month. On a day-to-day basis, it's difficult to understand where your money is being allocated, so seeing the big picture is helpful in understanding where you're spending too much.

Compare your grand total with the amount of income you bring in each month. You should have enough left over to feel comfortable contributing at least 10% of your income to savings each month, without feeling pinched. If you've noticed that you begin to get nervous toward the end of your pay period, you'll be able to see why based on this comparison.

Find ways to adjust your spending to save more. Common areas to cut back on are eating out and entertainment. Keep in mind that adjusting your spending doesn't have to mean cutting your favorite things out completely. For example, instead of eating lunch out every day, make it a weekly treat. Consider taking public transportation instead of driving. The benefits go beyond saving money: frugal choices are often healthier or better for the environment.