How to Build a Monthly Gas Budget (With Examples)

A step-by-step way to estimate monthly fuel spending from your commute and errands, and how to keep it on track when prices change.

Updated November 3, 2026

Gas is one of the few household costs that changes every week. A simple monthly budget helps you see what a price jump really means for you.

Step 1: Estimate monthly miles

• Commute: one-way distance × 2 × workdays per month (about 21).
• Errands and weekends: a typical household adds 200–400 miles a month.
• Trips: add any planned longer drives separately.

Example: a 15-mile commute → 15 × 2 × 21 = 630 miles, plus 300 miles of errands = 930 miles a month.

Step 2: Use your real MPG

The window-sticker number is usually optimistic. Reset your trip meter at a fill-up, drive normally, then divide miles by gallons at the next fill-up. Mixed city and highway driving is often 10–15% below the EPA combined rating.

Step 3: Multiply by today’s price

930 miles ÷ 25 mpg = 37.2 gallons × $4.269 (U.S. average, EIA, week of October 26, 2026) = about $159 a month.

Step 4: Add a buffer

Prices can move 20–40 cents in a few weeks. Adding a 10% buffer ($16 in the example) keeps your budget realistic. In the year to October 2026, regular rose about $1.23 a gallon – for this example, that is about $46 more every month.

Monthly budget at different prices

All at 25 mpg. Use our fuel calculators for your own figures, and the annual fuel cost guide for the yearly view.

Frequently asked questions