MPG Calculator

Your car's dashboard estimate is useful, but it is still an estimate. The only way to know your real MPG for a specific tank of gas is to measure it yourself, and it only takes one fill-up to do.

1. Fill your tank completely and reset your trip odometer, or note the current reading.
2. Drive normally until you are ready to fill up again, ideally at least 150 to 200 miles for an accurate reading.
3. Fill the tank again and record exactly how many gallons it took.
4. Enter the distance you drove and the gallons used into the MPG mode above to get your real-world fuel economy.

Miles per gallon and liters per 100 km measure the same thing in opposite directions. A higher MPG is better, since it means more distance per unit of fuel; a lower L/100km is better, since it means less fuel per unit of distance. To convert between them, divide 235.2 by the number you have, in either direction. This calculator's Fuel Economy field does that conversion automatically when you toggle its unit.

If you drive a typical annual distance and want to see what your fuel economy costs you over a full year rather than a single trip, the Miles Per Year Calculator turns your daily or weekly mileage into an annual total and estimated yearly fuel spend.

The MPG printed on a car's window sticker is an EPA lab estimate. Real-world mileage almost always differs, sometimes by a lot, depending on how and where you actually drive:

• Driving style: hard acceleration and braking can cut fuel economy noticeably compared to smooth, steady driving.
• Speed: fuel economy generally drops above 50 to 60 mph as air resistance increases.
• Short trips: a cold engine is less efficient, so frequent short trips lower average MPG more than one long trip of the same total distance.
• Extra weight and drag: cargo, roof racks, and towing all increase the fuel needed to move the vehicle.
• Tire pressure: underinflated tires increase rolling resistance and reduce MPG.
• Weather: cold weather and heavy use of climate control both tend to reduce real-world fuel economy.

Once you know your MPG, whether from your owner's manual or from the MPG mode above, the cost mode turns it into a real trip budget: enter your distance, your MPG, and the price per gallon at the pump, and it returns both the gallons you will need and the total cost. The comparison table below the result shows the same trip at a range of other common fuel-economy levels, which is useful if you are deciding between two vehicles or just curious what a more efficient car would have saved you. If you are also trying to plan arrival time alongside cost, the Drive Time Calculator covers that side of the same trip, and the Cost Per Mile Calculator breaks total vehicle cost down to a per-mile figure instead of a single trip total.

Not every mileage cost depends on fuel economy. Employers, some rental agreements, and the IRS all use a flat rate per mile instead, which covers gas plus wear, insurance, and depreciation in one number. The reimbursement mode above skips MPG and fuel price entirely: enter your distance and a rate per mile, and it multiplies the two directly.

• Work reimbursement: use the rate your employer specifies, often close to the IRS standard mileage rate.
• Tax deductions: self-employed drivers can deduct business miles at the IRS standard rate instead of tracking actual expenses.
• Rentals and leases: some agreements charge a flat per-mile rate once you exceed an included allowance.

This MPG calculator is part of a small family of driving-cost tools. These cover the other parts of the same trip:

• Cost Per Mile Calculator - break total vehicle cost down to a per-mile figure
• Drive Time Calculator - estimate arrival time and total driving time for the same trip
• Miles Per Year Calculator - turn your regular driving habits into an annual mileage and fuel-cost estimate
• Engine Hours to Miles Converter - convert engine-hour readings to an equivalent mileage for equipment and vehicles that track hours instead