By Kathryn Hauer, CFP, EA

Learn more about Kathryn on NerdWallet’s Ask an Advisor

It’s a good idea to have a budget, even if it’s an informal one. Some of us do pretty well with the fixed-cost part of the budget. Fixed costs are those that stay the same each month, like your rent or mortgage payment, cable package, gym membership, cell phone bill, car payment, the dating service you signed up for and can’t get out of. You know you’re going to have to pay the same amount each month, so you plan for it and cough it up regularly.

Your variable costs are harder to nail down, and those are the ones that can really blow your budget. A month of dining out a lot, buying a wedding present, replacing a muffler or paying your property tax bill, and your variable dollars are gone and then some.

These five tips will help you manage your variable expenses so you can stay on budget:

You’re pretty much committed to your rent, but you’ve got leeway in what you do with your other money each month. If you really enjoy that Starbucks every morning, it’s probably OK to get it. The first sip, and the 30 sips after that one, make you feel good — and feeling good is one of the key reasons we earn and spend money. However, other things you spend on may be more from habit than for pleasure. You might actually prefer bringing your lunch from home rather than eating yet another dejected hamburger from the work cafeteria, thereby reducing a variable expense. Evaluate your purchases and make sure they give you pleasure equal to what you spend on them.

One of the secrets to staying slim is to be mindful about what you eat. You’re supposed to ask yourself whether you really want that bag of M&M’s or whether an apple would be just as satisfying. (Yes, I do; no, it wouldn’t.) You can try to whittle down your expenses in the same way. Before you buy something, think about whether you really want or need it. Sometimes the act of pausing to think is enough to keep you from swiping your credit card.

It’s smart to look at the year ahead rather than just the month. Some expenses hit only every quarter (SiriusXM radio) or twice a year (dental cleaning copay). Other months offer the promise of reduced variable expenses (a week with generous in-laws at their lake house) or increased costs (because everyone in your family happened to be born in February). Acknowledging and accounting for the natural and regular seasonal variation in your expenses will help you better prepare for them, and may allow you to reduce them. 

Another great idea is to think about what you really want in terms of how much money you make. In our family, we say, “I like this sweater, but not $40 worth.” Or you can evaluate a dinner out or other expense based on the hours you’d work to pay for it. For instance, say your hourly rate after taxes is $18. A dinner charge of $80 means about four-and-a-half hours on the job for you.

Part of the problem with variable expenses is tracking them accurately. You know how much the rent is, but you may not be aware of how much you’re really spending on food, toiletries, gas, travel, gifts and the many other expenses that crop up. Advocacy site America Saves recommends keeping a record of expenses. You can use the simple, old-fashioned method of writing down your variable expenses in a notebook for a month or two, or you can go higher-tech. Use “Notes” on your phone or a mobile budgeting app like Mint or one of the many others NerdWallet recently reviewed.

To reduce your variable expenses successfully, you’ll need to pay attention to what you spend each day. That exercise can be tedious. It’s tiresome to have to watch, count and restrict yourself every day. However, over time your carefulness will come more easily and you’ll be more aware of the habits that increase your variable spending — and how to change them.

Kathryn Hauer, a certified financial planner, adjunct professor at Aiken Technical College and financial literacy educator, is the author of “Financial Advice for Blue Collar America.”

The article 5 Tips to Manage the Variable Costs in Your Budget originally appeared on NerdWallet.