Use measured fuel economy for a better estimate
A realistic input often improves a trip estimate more than extra decimal places.
By the TripFuel team · Updated November 3, 2026
Measure over a useful interval
If your vehicle records a recent average, check whether that average reflects driving similar to the journey you are planning. A long motorway average may not represent a week of short urban trips. To estimate economy manually, record distance travelled and fuel used over a consistent fill-to-fill interval. Divide miles by US gallons for US MPG, or divide litres by kilometres and multiply by 100 for L/100 km.
Do not confuse consumption with the gauge
A fuel gauge reading alone is a rough input because tank shapes and gauge behaviour vary. Partial fills can also make a single interval misleading. Several comparable intervals provide a more useful average. For 600 km using 42 litres, consumption is 42 ÷ 600 × 100 = 7 L/100 km. Enter that value with the L/100 km unit selected.
Treat the result as a range when needed
A single estimate does not capture all road conditions. Calculate once with your usual economy and again with a less efficient value to see the budget difference. You can copy or download each result for comparison. TripFuel does not access your location, identify your vehicle or fetch live prices. It calculates from the numbers you enter, so checking the distance, gallon type and return-trip setting is an essential final step.
Put the example into practice with the free fuel cost calculator.