Are fuel-consumption readings of 5 and 8 averaged to 6.5? Not for unequal distances
Consumption per 100 km must be weighted by distance. Averaging two dashboard figures equally can misrepresent the combined journey.
Fuel consumption →Add fuel and distance first
The first segment covers 100 km using five litres, while the second covers 400 km using thirty-two litres. Their consumption rates are 5 and 8 L/100km. Together they use thirty-seven litres over 500 km, giving 7.4 L/100km, not 6.5. Entering those combined quantities directly provides a straightforward verification.
Understand the weighting
The second segment contributes 80% of the total distance, so it should have more influence. The equivalent weighted calculation is 5 × 20% + 8 × 80% = 7.4. Only when the two distances are equal does a simple average of their consumption rates match the combined rate.
Fuel prices need a different weighting
If the fuel purchases have different prices per litre, calculate each purchase cost and add them. Do not automatically average two prices equally and multiply by the total volume. The fuel calculator takes one price at a time, so separate calculations preserve the detail of multiple purchases. Combined consumption is weighted by distance, while an effective average purchase price is weighted by litres. Keeping those denominators separate avoids turning a correct average in one context into an incorrect budget in another.
Try the calculators
- Fuel consumption
Estimate fuel consumption and cost.
- Average & median
Find the mean, median and sum of a list.
- Percentage change
Measure the change between two values.