Distance & Fuel Economy

Distance and fuel economy together

Travel maths mixes distance units with fuel economy units that depend on which gallon you mean. A UK mile-per-gallon figure is not the same as a US MPG figure even when both cars drive the same road, because the imperial gallon is larger than the US gallon. Metric countries usually quote litres per 100 kilometres (L/100 km) instead.

This page converts kilometres, statute miles, and nautical miles for distance, and links UK MPG, US MPG, and L/100 km for economy so road-trip planning and car adverts stay comparable.

Key factors

• 1 statute mile = 1.609344 kilometres (exact)
• 1 nautical mile = 1.852 kilometres (exact)
• Fuel economy conversions account for the UK vs US gallon when moving between MPG systems and L/100 km

Worked example

A journey of 100 miles (statute) is 160.934 km. A car rated 40 UK MPG uses less fuel per mile than a car rated 40 US MPG, because each UK gallon is larger; in L/100 km the UK figure converts to a lower (better) litres-per-distance number than the US figure of the same numeric MPG.

Which distance unit when

Use kilometres on metric road signs and most international maps. Use statute miles on US and UK road distance contexts (the everyday “mile”). Use nautical miles for aviation and marine navigation, where speed in knots already pairs with nautical miles per hour.

Common mistakes

• Comparing UK and US MPG as if the gallons matched.
• Treating lower L/100 km and higher MPG backwards — lower L/100 km is more efficient; higher MPG is more efficient.
• Mixing nautical miles into road trip estimates.

FAQs

Does this calculate trip fuel cost?

It converts units. For litres or gallons needed over a distance and rough cost, see also Trip Fuel.

Are statute miles the same as nautical miles?

No. A nautical mile is longer (1.852 km vs 1.609344 km).

Related: Trip Fuel, Liquids, Time Duration.