Miles per gallon (US) to Gallons per 100 miles (US)
mpg
gal/100mi (US)
Conversion History
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Quick Reference Table (Miles per gallon (US) to Gallons per 100 miles (US))
| Miles per gallon (US) (mpg) | Gallons per 100 miles (US) (gal/100mi (US)) |
|---|---|
| 15 | 271.120758044474564608412543736168 |
| 20 | 361.49434405929941947023080491326 |
| 25 | 451.867930074124274337575934287826 |
| 30 | 542.2415160889491291819633034575 |
| 40 | 722.988688118598838940036466119022 |
| 50 | 903.735860148248548675151868575652 |
| 55 | 994.109446163073403521664956282816 |
About Miles per gallon (US) (mpg)
Miles per gallon (US) — universally abbreviated mpg in the United States — is the dominant fuel economy metric in American automotive culture. Higher mpg means lower fuel consumption. The US gallon is 3.785 liters. The US Environmental Protection Agency (EPA) publishes city, highway, and combined mpg ratings on new vehicle window stickers, and Corporate Average Fuel Economy (CAFE) standards are set in mpg. Typical US passenger cars range from 15–20 mpg for trucks and large SUVs to 50–60 mpg for modern petrol hybrids. Because mpg is an efficiency unit (not consumption), the fuel savings from improving a low-mpg vehicle far exceed the savings from improving an already-efficient one.
A Ford F-150 pickup averages about 20 mpg combined on the EPA cycle. A Toyota Camry Hybrid achieves approximately 47 mpg combined.
About Gallons per 100 miles (US) (gal/100mi (US))
Gallons per 100 miles (US) — abbreviated gal/100mi — is a consumption metric, the American analogue to the European L/100km standard. Lower is better. It is the mathematical inverse of US mpg multiplied by 100. The US EPA introduced the GPM metric alongside mpg to help consumers make better fuel economy comparisons: because mpg is non-linear, the true fuel saving from improving a 15 mpg truck to 20 mpg (1.67 gal/100mi saved) is far larger than improving a 40 mpg car to 50 mpg (0.5 gal/100mi saved). GPM makes this intuitively clear by expressing absolute consumption rather than efficiency.
A 25 mpg family sedan consumes 4 gal/100mi. A 50 mpg hybrid uses only 2 gal/100mi — saving as much fuel per mile as the difference from 10 to 50 mpg on a low-efficiency vehicle.
Miles per gallon (US) – Frequently Asked Questions
Why is EPA mpg always higher than what I actually get?
The EPA tests cars on a dynamometer in a lab, not on real roads. While EPA adjusted its formulas in 2008 to be more realistic, factors like cold weather, air conditioning, aggressive driving, hilly terrain, and short trips still cause most drivers to underperform the sticker by 10–20%.
Why does the US use miles per gallon instead of L/100km?
The US never adopted the metric system for everyday use, and mpg has been embedded in American car culture since the 1970s oil crisis when fuel economy became a selling point. CAFE standards codified mpg into federal law, making a switch politically and practically difficult.
What is the "mpg illusion" and why does it matter?
The mpg illusion is the cognitive bias where people assume equal mpg improvements save equal fuel. In reality, upgrading a truck from 12 to 14 mpg saves more gallons over 10,000 miles than upgrading a sedan from 30 to 50 mpg. This is because mpg is a reciprocal measure — savings are concentrated at the low end.
How do I convert US mpg to UK mpg?
Multiply US mpg by 1.201 to get UK mpg (because the imperial gallon is 20.1% larger than the US gallon). A car rated 30 US mpg is about 36 UK mpg. Many Americans visiting the UK are confused when British cars seem to get impossibly high mpg numbers.
What is the highest mpg car ever sold in the US?
The 2025 Hyundai Ioniq Blue held the record for non-plug-in cars at 59 mpg combined. Among hybrids, the Toyota Prius has consistently led, reaching 57 mpg combined in recent model years. Plug-in hybrids running on electricity achieve MPGe ratings over 100, but that is a different metric entirely.
Gallons per 100 miles (US) – Frequently Asked Questions
Why did the EPA start showing gallons per 100 miles on window stickers?
Research by Duke University professors showed that mpg systematically misleads consumers about fuel savings. The EPA added gal/100mi to Monroney stickers starting in 2013 to give buyers a linear, comparable number. A 1 gal/100mi difference always represents the same fuel saving regardless of starting point.
How does gal/100mi help compare plug-in hybrids that switch between fuel and electricity?
Plug-in hybrids complicate mpg because they drive some miles on electricity and some on petrol. Gal/100mi lets you weight the two modes transparently: if a PHEV uses 0 gallons for its first 40 electric miles and 2.5 gal/100mi after that, fleet managers can model exact fuel costs for any commute length. The EPA's MPGe tries to do something similar for consumers, but gal/100mi is more intuitive for mixed-mode budgeting.
What gal/100mi does the average American car use?
The average new car in the US uses about 3–4 gal/100mi (25–33 mpg). Full-size trucks sit around 5–7 gal/100mi, while hybrids achieve 1.5–2.5 gal/100mi. Electric vehicles show 0 gal/100mi but have a separate kWh/100mi rating.
Why do long-haul trucking companies obsess over fractions of a gal/100mi?
A Class 8 semi averages about 6.5 gal/100mi and covers 100,000+ miles per year — roughly 6,500 gallons annually. Shaving just 0.3 gal/100mi through aerodynamic fairings, low-rolling-resistance tires, or driver coaching saves ~300 gallons per truck per year. Across a 5,000-truck fleet, that is 1.5 million gallons saved — worth over $5 million at US diesel prices. At that scale, every tenth of a gal/100mi is a budget line item.
Why do Europeans never use gal/100mi even though they use L/100km?
Europeans adopted L/100km as their native metric from the start, so there was never a need for an alternative. Gal/100mi was invented specifically to fix the mpg illusion problem in the US. Europeans already had the "right" unit — they just used metric volumes and distances.