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Fuel Consumption Calculator

Calculate liters, gallons, and cost of fuel consumed for any distance.

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Understanding Fuel Consumption

Consumption Formula

Fuel Consumed (L) = Distance (km) ÷ 100 × Fuel Efficiency (L/100 km). A car using 9 L/100 km over 400 km consumes 36 liters — costing $59.40 at $1.65/L.

Unit Conversions

1 liter = 0.2642 US gallons = 0.2200 UK gallons. The UK gallon is larger (4.546 L vs 3.785 L for US), so UK mpg figures are higher than US mpg for the same vehicle.

What Affects Consumption

Speed, acceleration habits, tyre pressure, vehicle load, air conditioning, road gradient, and weather all affect real-world fuel consumption by 10–30% vs. manufacturer ratings.

CO₂ Calculation

CO₂ (kg) = Liters burned × CO₂ factor (kg/L). Petrol: 2.31 kg/L, Diesel: 2.68 kg/L, E85: 1.48 kg/L. Lower fuel consumption directly reduces your carbon footprint.

Core Fuel Cost Formulas

Trip Fuel Cost

Cost = (Distance ÷ 100) × L/100km × Price/L

Most widely used formula — works in any currency

Fuel Consumed

Liters = (Distance ÷ 100) × L/100km

Multiply by 0.2642 for US gallons, 0.2200 for UK gallons

L/100km → mpg US

mpg(US) = 235.214 ÷ L/100km

1 US gallon = 3.785411784 liters

L/100km → mpg UK

mpg(UK) = 282.481 ÷ L/100km

1 UK gallon = 4.54609 liters (20% larger than US gallon)

CO₂ Emissions

CO₂ (kg) = Fuel (L) × Emission Factor (kg/L)

Petrol: 2.31 | Diesel: 2.68 | Hybrid: 1.85 | E85: 1.48

Fleet Daily Cost

Fleet Cost = Vehicles × (km/day ÷ 100) × L/100km × Price/L

Multiply by operating days for annual figure

Fuel Saving Best Practices

Maintain Optimal Speed

Highway speeds of 90–100 km/h (55–62 mph) use 15–20% less fuel than 120 km/h. Above 100 km/h, aerodynamic drag increases exponentially.

Check Tyre Pressure Monthly

Under-inflated tyres increase rolling resistance. Correct pressure improves fuel economy by 0.5–3% and extends tyre life significantly.

Remove Unnecessary Weight

Every 50 kg of extra weight reduces fuel economy by ~1–2%. Remove roof racks, trailers, and heavy items from the boot when not needed.

Smooth Acceleration & Braking

Aggressive acceleration and late braking can increase fuel consumption by 20–30%. Anticipate traffic and coast to decelerate wherever possible.

Use Air Conditioning Wisely

A/C increases fuel consumption by 5–25% depending on conditions. At lower speeds, open windows; at highway speeds, closed windows with A/C is more efficient.

Service Your Vehicle Regularly

Fresh engine oil, clean air filters, and correctly gapped spark plugs keep your engine running at peak efficiency. A dirty air filter alone reduces fuel economy by up to 10%.

Why Fuel Costs Matter

Household Budgets

The average household spends $2,000–$5,000 per year on fuel. Even a 10% efficiency improvement generates meaningful savings that compound over vehicle ownership years.

Business Operations

Fuel is often the second largest operating cost for transport businesses after labor. Fleet fuel management, route optimization, and driver training deliver measurable ROI within months.

Environmental Impact

Transport accounts for ~25% of global CO₂ emissions. Choosing fuel-efficient vehicles, combining trips, and transitioning to hybrids or EVs directly reduces per-journey carbon footprint.

Common Fuel Cost Mistakes

Using manufacturer fuel economy ratings

Official fuel economy figures are measured in laboratory conditions. Real-world consumption is typically 10–30% higher. Use your own measured fill-up data for accurate calculations.

Forgetting unit differences

UK mpg and US mpg are NOT the same — a UK mpg reading is ~20% higher than US mpg for the same car. The British Imperial gallon (4.546 L) is larger than the US gallon (3.785 L).

Ignoring seasonal variation

Fuel consumption increases 10–20% in winter due to cold engine inefficiency, lower tyre pressure, heavier loads, and more frequent use of heating and lights.

Comparing petrol and diesel prices directly

Diesel typically costs more per liter but delivers 25–30% better fuel economy. Compare the cost per km, not the price at the pump, to determine which is cheaper to run.

About This Fuel Cost Calculator

Accurate Formulas

Built on internationally recognized unit conversions (US & UK gallons) and IPCC CO₂ emission factors for petrol, diesel, hybrid, E85, and biofuels.

Free & Private

All calculations run in your browser. No personal data, location, or vehicle details are sent to any server.

Engineer Verified

Fuel efficiency conversions cross-checked against NIST unit definitions and EPA fuel economy standards.

Related tools: Speed Calculator, Unit Converter, Budget Calculator, Tire Size Calculator, Horsepower Calculator.

Frequently Asked Questions

Fuel Cost = (Distance ÷ 100) × L/100 km × Fuel Price per Liter. For a 500 km trip in a car using 8 L/100 km at $1.60/L: (500 ÷ 100) × 8 × 1.60 = $64. Enter your values in the Trip Fuel Cost calculator above to get an automatic result in any unit combination.

Fuel efficiency measures how far a vehicle travels on a given amount of fuel. It is expressed in different units by region: L/100 km (liters per 100 kilometers) in Europe and Australia — lower is better; km/L (kilometers per liter) in Asia and Latin America — higher is better; mpg US (miles per US gallon) in the United States — higher is better; mpg UK (miles per Imperial gallon) in the United Kingdom — higher is better. A typical family car achieves 7–10 L/100 km or 25–35 mpg US.

Fuel Needed = (Distance ÷ 100) × L/100 km. For 500 km in a car consuming 8 L/100 km: (500 ÷ 100) × 8 = 40 liters (10.6 US gallons). An economy car at 6 L/100 km would need only 30 liters for the same journey, saving roughly $16.50 at $1.65/L fuel prices.

The US gallon contains 3.785 liters while the UK (Imperial) gallon contains 4.546 liters — approximately 20% larger. This means a car rated at 30 mpg US actually achieves about 36 mpg UK. When comparing manufacturer fuel economy figures, always check which gallon standard was used. Conversion: mpg UK = mpg US × 1.2009. Our fuel efficiency converter automatically handles both standards.

CO₂ Emissions (kg) = Fuel Consumed (liters) × Emission Factor (kg/L). Emission factors vary by fuel type: petrol 2.31 kg/L, diesel 2.68 kg/L, premium petrol 2.31 kg/L, hybrid 1.85 kg/L, E85 ethanol 1.48 kg/L, biofuel 0.65 kg/L. For a 500 km petrol trip using 40 liters: 40 × 2.31 = 92.4 kg CO₂. These factors align with IPCC and UK DEFRA greenhouse gas reporting guidelines.

Driving speed has the largest single impact — fuel consumption increases exponentially above 100 km/h (62 mph) due to aerodynamic drag. Other key factors: driving style (aggressive acceleration and braking increase consumption 20–30%); tyre pressure (under-inflation increases rolling resistance by 3–5%); vehicle load (every 50 kg adds ~1% fuel use); air conditioning (adds 5–25%); road gradient; engine temperature; and ambient temperature (cold engines use 10–20% more fuel until fully warmed). Manufacturer fuel economy ratings are tested in controlled conditions and can be 10–30% optimistic versus real-world driving.

The most effective strategies: (1) Drive at optimal highway speeds of 90–100 km/h — this alone can reduce fuel use by 15–20% vs 120 km/h. (2) Accelerate and brake smoothly — aggressive driving wastes 20–30% more fuel. (3) Keep tyres properly inflated — saves 1–3%. (4) Remove roof racks and reduce vehicle weight when not needed. (5) Service your vehicle regularly — fresh oil and clean air filters prevent efficiency losses of 5–10%. (6) Combine trips — a cold engine uses 50% more fuel for the first few minutes. (7) Consider a fuel-efficient vehicle if your current car is over 10 years old.

To convert L/100 km to mpg US: divide 235.214 by your L/100 km figure. Example: 8 L/100 km = 235.214 ÷ 8 = 29.4 mpg US. To convert to mpg UK: divide 282.481 by your L/100 km figure. Example: 8 L/100 km = 282.481 ÷ 8 = 35.3 mpg UK. To convert mpg US back to L/100 km: divide 235.214 by the mpg value. Use the Fuel Efficiency Converter tab above for instant multi-unit conversions.

Diesel vehicles typically cost more per liter at the pump but achieve 25–35% better fuel economy than equivalent petrol engines. The true comparison is cost per km (or per mile), not price per liter. Calculate: Cost/km = (L/100 km × Fuel Price) ÷ 100. If a diesel car achieves 6 L/100 km at $1.85/L: $0.111/km. A petrol equivalent at 8 L/100 km at $1.65/L: $0.132/km. In this example, diesel is cheaper to run despite the higher pump price. Use the Fuel Price Comparison tab to model your specific situation.

Fleet Daily Cost = Number of Vehicles × (Daily Distance per Vehicle ÷ 100) × L/100 km × Fuel Price per Liter. For 20 trucks driving 150 km/day at 12 L/100 km and $1.72/L: 20 × (150 ÷ 100) × 12 × 1.72 = $619.20 per day. Multiply by annual operating days (typically 250 workdays) for annual fleet fuel budget: $154,800/year. The Fleet Fuel Cost Calculator automates this and adds CO₂ reporting for sustainability disclosures.

Fuel economy ratings vary significantly by vehicle class. In L/100 km: under 5 is exceptional (small hybrids, electric-range extenders); 5–7 is excellent (economy cars, efficient sedans); 7–10 is average (family sedans, small SUVs); 10–14 is below average (larger SUVs, pickup trucks); over 14 is poor (heavy trucks, performance cars). In US mpg: above 50 is exceptional; 35–50 is excellent; 25–35 is average; 18–25 is below average; under 18 is poor. EPA fuel economy leaders in 2024 include hybrids averaging 50+ mpg US and plug-in hybrids with 80+ mpge combined.

Round Trip Fuel Cost = One-Way Fuel Cost × 2. Example: if a 300 km one-way trip costs $42 in fuel, the round trip costs $84. You can also use our calculator with the Round Trip toggle enabled — it automatically doubles the distance before calculating fuel volume and cost, giving you an accurate total without manual multiplication. This also doubles the CO₂ emissions estimate, which is useful for environmental reporting.

US Gallons = (Distance in km ÷ 100) × L/100 km ÷ 3.785411784. Or if using miles and mpg US: Gallons = Distance in miles ÷ mpg US. Example: 300 miles at 32 mpg = 9.375 US gallons. UK Gallons = Liters ÷ 4.54609. These conversions allow you to compare fuel efficiency and costs regardless of which measurement system you're using.

Cost per 100 km = L/100 km × Fuel Price per Liter. For a car using 9 L/100 km at $1.65/L: 9 × $1.65 = $14.85 per 100 km. Over 15,000 km/year, this amounts to $2,227 in annual fuel costs. Improving efficiency by 2 L/100 km (switching from 9 to 7 L/100 km) saves $3.30 per 100 km — $495 per year at the same mileage.

E85 is a blend of 85% ethanol and 15% petrol, used in flex-fuel vehicles. Ethanol has a lower energy density than petrol, so E85 vehicles consume approximately 25–30% more fuel by volume to travel the same distance. However, E85 often sells for 15–30% less than petrol per liter. The net fuel cost depends heavily on local price differentials. E85 has a lower CO₂ emission factor (1.48 kg/L vs 2.31 kg/L for petrol) because the ethanol portion comes from renewable plant sources, making it better for carbon footprint calculations.

SUV fuel consumption varies widely by size and powertrain. Compact SUVs (e.g., Toyota RAV4): 7–9 L/100 km; Mid-size SUVs (e.g., Ford Explorer): 9–12 L/100 km; Full-size SUVs (e.g., Chevy Suburban): 12–16 L/100 km; Hybrid SUVs (e.g., Toyota RAV4 Hybrid): 5–7 L/100 km. Real-world consumption depends significantly on city vs highway driving, passenger load, and climate. City driving typically increases SUV consumption by 20–40% over highway figures.

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