Gas Mileage & Trip Cost Calculator (MPG)
Two tools in one: compute your real MPG from a fill-up, and estimate any trip's fuel cost from distance, MPG and gas price.
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1 · What is my MPG?
2 · Trip Cost
Knowing Your Real MPG
The honest method: fill the tank, reset the trip odometer, drive normally, fill again — MPG = miles driven ÷ gallons refilled. 348 miles on 12.4 gallons is 28.1 MPG. Average two or three tanks; a single reading swings with pump click-off points. Trip cost then follows: gallons = distance ÷ MPG, cost = gallons × price — 1,200 highway miles at 28 MPG and $3.50/gal runs $150.
Real-world MPG typically lands 10-15% under the EPA window sticker, worse in winter, city stop-and-go, roof racks and speeds over 70 mph. Metric drivers: L/100 km = 235.21 ÷ MPG.
Frequently Asked Questions
Why did my MPG drop suddenly?
Usual suspects in order: winter fuel blends and cold starts, low tire pressure, short trips that never warm the engine, a dirty air filter, dragging brakes. A sustained unexplained drop is worth a mechanic's look.
Does premium gas improve MPG?
Only in engines that require or specifically tune for it. In a regular-fuel engine premium buys nothing measurable — the octane rating is knock resistance, not energy content.
How do I split fuel cost on a road trip?
Total cost ÷ people. The cost-per-mile output also lets you charge fair partial-leg shares.
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Gas Mileage & Trip Cost Calculator (MPG)