Tank Range Calculator
Calculate your vehicle's maximum driving range from tank size and fuel economy.
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What this tool does
This calculator estimates the maximum driving range of a vehicle by converting tank capacity in litres to UK gallons (using the conversion factor 4.54609 L/gallon) and multiplying by fuel economy in UK MPG. Inputs are tank size (litres) and MPG (UK); the output is theoretical range in miles and kilometres. The result assumes the entire tank is usable and that the stated MPG figure is achieved consistently throughout the journey.
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Formula
How Tank Range Calculator works
The calculator converts a fuel tank's capacity from litres into UK gallons, then multiplies by the vehicle's fuel economy figure (UK MPG) to produce a theoretical maximum range. The output shows both miles and kilometres, representing the distance the vehicle could travel if the entire tank were consumed at the specified economy rate.
The formula
The calculation proceeds in two steps:
- Tank in UK gallons = Tank (litres) ÷ 4.54609
- Range (miles) = UK gallons × MPG (UK)
For the kilometre figure, the mile result is multiplied by 1.609344. The constant 4.54609 is the official litre-to-UK-gallon conversion used throughout the United Kingdom.
Where this method is most accurate
This estimate is most useful when the stated MPG figure reflects real-world driving conditions and the entire tank volume is genuinely usable. Many vehicles reserve a small portion of tank capacity below the low-fuel warning light, and real-world economy often differs from manufacturer combined-cycle figures. The calculation assumes constant fuel economy across the entire journey; in practice, economy varies with speed, terrain, temperature, and driving style.
What this tool does not do
The calculator does not account for reserve fuel, variations in fuel density, or real-time driving conditions. It does not verify whether the stated MPG is achievable, nor does it incorporate safety margins for fuel-station spacing. The tool performs a straightforward mathematical conversion and does not provide route-planning advice or guarantee that any specific journey is feasible on a single tank.
Disclaimer
This calculator is provided for educational and estimation purposes only. It does not constitute vehicle operation advice, journey-planning guidance, or a guarantee of achievable range. Real-world fuel consumption varies with driving behaviour, weather, load, and road conditions. Always consult the vehicle handbook and plan refuelling stops with an appropriate safety margin.
Questions
- Why does this calculator use UK gallons instead of US gallons?
- The tool explicitly accepts UK MPG as input. A UK (imperial) gallon is 4.54609 litres, whereas a US gallon is 3.78541 litres. Mixing US MPG with the UK gallon conversion—or vice versa—will produce incorrect range estimates.
- Does the calculator account for reserve fuel below the warning light?
- No. The calculation assumes the entire stated tank capacity is usable. Most vehicles retain 1–3 litres below the low-fuel warning, meaning practical range is slightly less than the calculated figure.
- Can I use manufacturer combined-cycle MPG figures?
- Combined-cycle MPG is an average of urban and extra-urban test results. Real-world economy often differs. The calculator will compute range based on whatever MPG value is entered, but the result is only as accurate as the input figure.
- Why might my actual range differ from the calculator's output?
- Fuel economy varies with driving style, speed, load, tyre pressure, temperature, and terrain. The calculator performs a theoretical multiplication; it cannot anticipate traffic, headwinds, air-conditioning use, or other real-world factors that affect consumption.
- How do I convert my car's MPG if it is displayed in litres per 100 km?
- To convert L/100 km to UK MPG, divide 282.481 by the L/100 km figure. For example, 6.0 L/100 km equals approximately 47.1 UK MPG. Once converted, enter that MPG value into this calculator alongside the tank size.
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Sources & Methodology
The engine converts tank capacity (litres) to UK gallons by dividing by 4.54609 L/gallon, then multiplies by UK MPG to yield range in miles. Kilometres are derived by multiplying miles by 1.609344. The UK gallon conversion constant is defined by UK Weights and Measures Act 1985.
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