Practical guide
Fuel consumption, journey cost and tire size — how are they calculated?
Automotive calculators combine measured data with simple geometry. A result helps compare consumption or dimensions but does not replace vehicle documentation or technical assessment.
Consumption needs a complete measurement
A good simple measurement uses fuel added to a comparable fill level and distance since the previous fill. Divide litres by kilometres and multiply by 100.
One result depends on route, weather and driving style, so average several fills.
Journey cost uses forecast consumption
Required litres come from distance and l/100 km, while cost uses price per litre. A return journey needs total distance, not the one-way value.
Add tolls and parking separately when preparing a complete travel budget.
Tire size describes geometry
Notation such as 205/55 R16 gives width, profile percentage and rim diameter. Nominal diameter affects circumference and the speedometer relationship.
Similar diameter does not confirm approval or fitment: check rim width, offset, load and speed ratings and clearance.
Frequently asked questions
What does this guide explain about “Consumption needs a complete measurement”?
A good simple measurement uses fuel added to a comparable fill level and distance since the previous fill. Divide litres by kilometres and multiply by 100. One result depends on route, weather and driving style, so average several fills.
What does this guide explain about “Journey cost uses forecast consumption”?
Required litres come from distance and l/100 km, while cost uses price per litre. A return journey needs total distance, not the one-way value. Add tolls and parking separately when preparing a complete travel budget.
What does this guide explain about “Tire size describes geometry”?
Notation such as 205/55 R16 gives width, profile percentage and rim diameter. Nominal diameter affects circumference and the speedometer relationship. Similar diameter does not confirm approval or fitment: check rim width, offset, load and speed ratings and clearance.
Calculators covered by this guide
Tire size calculator
Compare two tire sizes by diameter, clearance and indicated speed difference.
Fuel consumption calculator
Calculate average fuel use in litres per 100 kilometres.
Fuel cost calculator
Estimate fuel required for a journey and the total fuel cost.