Fuel Cost Calculator | Trip Cost & CO2
Calculate trip fuel cost from distance, fuel efficiency, and price per litre. Supports L/100km, km/L, MPG US/UK, six currencies, CO2 estimate, and step-by-step working.
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What Is the Fuel Cost Calculator | Trip Cost & CO2?
The fuel cost calculator converts your trip distance, vehicle efficiency, and local fuel price into a precise cost estimate. All calculations run live in the browser, no data is sent to any server. The core formula is deceptively simple: multiply your distance in km by your consumption rate in L/100km, divide by 100 to get litres used, then multiply by price per litre.
The calculator supports four efficiency units, L/100km (most of the world), km/L (South and Southeast Asia),MPG US (United States), and MPG UK (United Kingdom and older Commonwealth standards). All are internally converted to L/100km for consistent computation, with the conversion formulas shown in the formula box above.
The CO' estimate uses the standard factor of 2.31 kg CO' per litre for petrol (gasoline). Diesel is slightly higher at 2.68 kg/L. This figure represents tailpipe emissions only and does not include upstream extraction and refining.
Formula
How to Use
- 1Choose what to solve for: Select Total Cost, Cost per km, Fuel Needed, or Max Distance using the tabs at the top.
- 2Load a preset (optional): Click any quick preset, City commute, Highway trip, Weekend drive, etc., to populate all fields instantly.
- 3Enter your distance: Type the trip distance and select km or miles. Enable Round trip to automatically double the distance.
- 4Enter fuel efficiency: Type your vehicle's fuel consumption and choose the unit: L/100km, km/L, MPG (US), or MPG (UK). Check your car's manual or a previous fuel receipt.
- 5Set the fuel price: Enter the current pump price per litre and select your currency (USD, EUR, GBP, INR, AUD, or CAD).
- 6Press Calculate: Click the Calculate button or press Enter. Results appear instantly showing total cost, fuel volume, cost per km, and CO₂ estimate.
- 7Expand step-by-step: Click "Step-by-step working" to see each calculation substituted with your actual numbers, useful for checking or learning.
- 8Copy results: Use the "Copy results" button to paste the summary into any document, spreadsheet, or messaging app.
Example Calculation
Example 1, European road trip (L/100km)
Distance: 800 km • Efficiency: 6.5 L/100km • Price: €1.75/L
Fuel = 800 km × 6.5 / 100 = 52 L
Cost = 52 L × €1.75 = €91.00
Cost per km = €91.00 / 800 = €0.1138/km
CO² = 52 × 2.31 = 120.12 kg
Example 2, US highway trip (MPG US)
Distance: 350 miles • Efficiency: 32 MPG • Price: $3.45/gallon
MPG US → L/100km: 235.215 / 32 = 7.35 L/100km
Miles → km: 350 × 1.60934 = 563.3 km
Fuel = 563.3 × 7.35 / 100 = 41.40 L
Price/L: $3.45 / 3.785 = $0.9113/L
Cost = 41.40 × $0.9113 = $37.73
Example 3, Daily commute budget (km/L)
Distance: 25 km • Efficiency: 12 km/L • Price: £1.60/L • Round trip
Total distance = 25 × 2 = 50 km (round trip)
km/L → L/100km: 100 / 12 = 8.333 L/100km
Fuel = 50 × 8.333 / 100 = 4.167 L
Cost = 4.167 × £1.60 = £6.67/day
Monthly (22 days) = £146.67
Understanding Fuel Cost | Trip Cost & CO2
Understanding Fuel Costs
Fuel is typically the second-largest cost of vehicle ownership after depreciation. Understanding the true per-kilometre cost helps with budgeting road trips, comparing vehicles before purchase, and evaluating whether a more fuel-efficient car justifies the price premium. All calculations in this tool run entirely in your browser, no data leaves your device.
Efficiency Units Explained
- L/100km, used across Europe, Australia, Canada, and most of the world. Lower is more efficient. Most modern cars range from 5 to 12 L/100km.
- MPG (US), miles per US gallon. Used in the United States. Higher is more efficient. City cars: 25–35 MPG; hybrids: 50+ MPG.
- MPG (UK), miles per Imperial gallon. The UK gallon is 4.546 L vs 3.785 L for US, so UK MPG is always numerically higher for the same car.
- km/L, common in South Asia, Southeast Asia, and Latin America. Directly analogous to MPG but in metric units.
Factors That Affect Real-World Consumption
- Speed: Most cars achieve best efficiency at 80–100 km/h. Driving at 130 km/h uses 20–30% more fuel than at 100 km/h due to aerodynamic drag scaling with the square of speed.
- Load: Every 100 kg of extra weight increases consumption by roughly 0.7 L/100km. Pack light for long trips.
- Acceleration style: Aggressive acceleration and hard braking can reduce efficiency by 15–30%. Smooth driving with anticipatory braking is the single biggest behavioural factor.
- Air conditioning: AC adds 1–2 L/100km in city driving, less at highway speeds where the aerodynamic cost of open windows exceeds AC usage.
- Cold weather: Engine efficiency drops until the engine reaches operating temperature. Short trips in cold weather see disproportionately high consumption.
Trip Comparison and Budgeting
Use the presets to quickly benchmark different scenarios. For regular commuters, even a small improvement in efficiency (say from 9.5 to 8.5 L/100km) on a 40 km daily round trip saves approximately 146 litres per year, over $270 at typical European prices. This kind of calculation makes the economics of hybrid or electric vehicles concrete.
Frequently Asked Questions
How do I convert between L/100km and MPG?
The two units are reciprocals (one measures consumption, the other efficiency), so they require division rather than multiplication:
- • US MPG: 235.215 / L100km e.g. 8 L/100km = 29.4 MPG US
- • UK MPG: 282.481 / L100km (UK uses imperial gallons)
- • km/L: 100 / L100km e.g. 8 L/100km = 12.5 km/L
This calculator handles all conversions internally, just pick your unit and enter the value directly.
Why do fuel costs increase so much on city roads vs highways?
Stop-start driving burns fuel without covering distance. Each time you brake, kinetic energy is lost as heat. Reaccelerating from rest is the most fuel-intensive moment of driving.
- • City driving typically adds 30–50% more fuel consumption than highway figures
- • Idling at traffic lights consumes 0.5–0.8 L/hour
- • Air conditioning adds ~10% to fuel use in city conditions
Use the worst-case (city) efficiency value when budgeting for urban commutes.
Can I use this calculator for diesel or electric vehicles?
Yes to both. For diesel, the calculation is identical, enter your diesel consumption rate and diesel price. Note: diesel CO' per litre is 2.68 kg (vs 2.31 kg for petrol).
- • Electric vehicles: enter kWh/100km as the “efficiency” and price per kWh as the “fuel price”
- • Hybrid vehicles: use real-world combined consumption figures
- • LPG/CNG: enter consumption in L/100km and price per litre
What does the CO2 estimate mean and how accurate is it?
The CO' figure shows tailpipe emissions for your trip. The calculator uses 2.31 kg CO²/L for petrol, which is the standard IPCC/EU factor based on combustion chemistry.
- • Diesel: 2.68 kg/L • E10 petrol: ~2.24 kg/L
- • This covers tailpipe emissions only (Scope 1)
- • Lifecycle emissions including extraction and refining are roughly 20% higher
How does the round trip toggle work?
When you enable “Round trip”, the calculator doubles your entered distance before computing fuel and cost. This assumes the return journey has the same route and conditions.
If your return trip differs significantly (e.g. different elevation or load), calculate each leg separately and add the results.
What is the "Solve for" feature?
Normally you solve for Total Cost given distance, efficiency, and price. The Solve for tabs let you rearrange the formula:
- • Cost per km: how much each kilometre costs you
- • Fuel Needed: volume of fuel for the trip
- • Max Distance: how far you can go on a set budget
How does tyre pressure affect fuel consumption?
Under-inflated tyres increase rolling resistance, raising fuel consumption by 0.5–3% per PSI below optimal. A tyre 8 PSI under-inflated (a common real-world condition) can cost you an extra 3% in fuel over the whole trip.
Check tyre pressure before any long trip, it is one of the easiest free fuel-saving measures.
Is this calculator accurate for trip planning?
It is accurate given the inputs you provide. Real-world variations include:
- • Vehicle load (passengers and luggage add weight)
- • Elevation change (climbing consumes more fuel)
- • Wind and temperature (cold engines and headwinds increase consumption)
- • Driving speed (most cars are most efficient at 80–90 km/h)
Add a 10–15% buffer to your estimate for real-world conditions.