Example: MPG to L/100 km
Convert 30 MPG (US) to L/100 km.
Formula: L/100 km = 235.214583 ÷ MPG
Calculation: 235.214583 ÷ 30 = —
Fuel Economy & Efficiency
Fuel Economy & Efficiency Unit Converter
Convert Fuel Economy (MPG US/UK, km/L, L/100 km), Fuel Consumption, Energy per Distance, CO₂ per Distance, Fuel Cost, Tank Capacity, Range per Tank, plus engine metrics like BSFC, Specific Fuel Consumption, Thermal Efficiency and Emission Rate.
L/100km ↔ MPG (US/UK)
Cost/mi = (price/gal) ÷ MPG
Range = Tank × MPG
BSFC (g/kWh ↔ lb/(hp·hr))
gCO₂/km ↔ gCO₂/mi
kWh/100km ↔ Wh/mi
Direct vs inverse
MPG and km/L are distance per fuel (bigger is better). L/100 km is fuel per distance (smaller is better).
Costs need inputs
Cost per distance or trip cost requires a fuel price and a mileage value. This page converts units and can compute costs when you provide them.
Energy and emissions
Includes energy-per-distance formats used by EVs (Wh/mi, kWh/100 km) plus CO₂ and emission rate unit conversions.
Interactive Converter
Pick a category, choose units, enter a value, then copy the result. Use Swap to reverse units.
Category explanation
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Select a category to see what it means and where it is used.
Base unit: —
Plain language
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Common formula
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Real world uses
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Optional: Fuel Price
Used for cost per distance and trip cost.
Optional: Trip Distance
Used for trip fuel and trip cost.
Optional: Tank Size
Used for range per tank (with mileage).
Tip: US MPG ≠ UK MPG. UK MPG is higher because the UK gallon is larger.
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Enter a value to convert
Optional calculations (when inputs are provided)
Cost per distance: —
Trip fuel and trip cost: —
Range per tank: —
These calculations use the current "Mileage / Distance per Fuel / Fuel per Distance" value when selected.
Conversion Formula
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Notes: MPG ↔ L/100 km is an inverse relationship. Cost and range results depend on the extra inputs above.
Visual Comparisons & Charts
See how different fuel economy units compare visually. These charts help you understand the relationships between MPG, L/100 km, and other metrics.
MPG (US) vs L/100 km Relationship
Shows the inverse relationship: as MPG increases, L/100 km decreases. Both represent the same efficiency, just measured differently.
Fuel Cost per 100 Miles (at $3.50/gal)
Demonstrates how fuel economy directly impacts your driving costs. Better efficiency = lower cost per distance.
CO₂ Emissions per 100 Miles
Vehicle efficiency directly correlates with carbon emissions. Better MPG means lower environmental impact.
Range per Tank (15 gallon tank)
How far you can travel on a full tank depends on both tank size and fuel economy. Better efficiency extends your range.
Worked Examples
Examples help visitors sanity check results (US vs UK MPG, energy formats, CO₂ per distance).
Example: CO₂ per distance
Convert 180 g/km to g/mi.
Formula: g/mi = g/km × 0.621372
Calculation: 180 × 0.621372 = —
Example: BSFC
Convert 250 g/kWh to lb/(hp·hr).
Formula: lb/(hp·hr) = g/kWh × 0.001328
Calculation: 250 × 0.001328 = —
Example: Fuel Cost per Mile
Calculate cost/mile at 25 MPG with $3.50/gal fuel.
Formula: Cost/mi = Price/gal ÷ MPG
Calculation: $3.50 ÷ 25 = —
Example: Trip Fuel & Cost
Calculate fuel and cost for 300 mile trip at 30 MPG, $3.50/gal.
Formula: Fuel = Distance ÷ MPG, Cost = Fuel × Price
Calculation: 300 ÷ 30 = — gal, Cost = —
Example: Range per Tank
Calculate range with 15 gallon tank at 28 MPG.
Formula: Range = Tank × MPG
Calculation: 15 × 28 = — miles
Quick Reference Table
Common fuel economy conversions and their equivalents.
| MPG (US) | MPG (UK) | km/L | L/100 km | Efficiency Level |
|---|---|---|---|---|
| 15 | 18.0 | 6.38 | 15.68 | Poor |
| 20 | 24.0 | 8.51 | 11.76 | Below Average |
| 25 | 30.0 | 10.64 | 9.40 | Average |
| 30 | 36.0 | 12.77 | 7.84 | Good |
| 40 | 48.0 | 17.03 | 5.88 | Excellent |
| 50 | 60.0 | 21.28 | 4.70 | Outstanding |
FAQ
Why does L/100 km go down when MPG goes up?
L/100 km is fuel used to travel a fixed distance. Better efficiency uses fewer liters for 100 km, so the number gets smaller. It's the inverse of MPG (distance per fuel).
US MPG vs UK MPG?
UK MPG uses the Imperial gallon (4.546 L) which is larger than the US gallon (3.785 L). That makes UK MPG numerically higher for the same vehicle. A car getting 30 MPG (US) gets about 36 MPG (UK).
What is BSFC?
Brake Specific Fuel Consumption is fuel mass per power output (g/kWh or lb/(hp·hr)). Lower BSFC generally means better engine efficiency. It's used in engine maps and performance analysis.
How do I calculate fuel cost for a trip?
Use the formula: Trip Cost = (Trip Distance ÷ MPG) × Fuel Price per Gallon. For example, a 300-mile trip at 30 MPG with $3.50/gallon fuel costs: (300 ÷ 30) × $3.50 = $35.
What is the relationship between fuel economy and CO₂ emissions?
Better fuel economy means lower CO₂ emissions per distance traveled. Burning less fuel produces less carbon dioxide. A vehicle with 30 MPG produces less CO₂ per mile than a vehicle with 20 MPG.
How is range per tank calculated?
Range = Tank Size × Fuel Economy. For example, a 15-gallon tank with 28 MPG gives a range of 15 × 28 = 420 miles. This assumes the tank is completely full.