Fuel calculator
Fuel Cost per 100 km
Estimate fuel used and cost for 100 km using UK MPG and your fuel price.
Use this calculator
What your result means
This is the estimated fuel-only cost to drive 100 km at the UK MPG and pump price entered. It turns an efficiency figure into a fixed-distance spending figure, which can be easier to compare than a journey total.
Higher UK MPG lowers litres used for the same distance. The calculation uses the UK imperial gallon, so do not enter a US MPG figure without converting it first.
Worked example
At 45 UK MPG and 145p per litre, for 100 km:
- Fuel used
- 6.3 litres
- Estimated cost
- £9.10
- Cost per mile
- 14.6p
It is a transparent estimate from the two inputs, not a fuel-price forecast.
Formula
How UK MPG changes cost for 100 km
| UK MPG | Fuel used | Estimated cost |
|---|---|---|
| 30 | 9.4 litres | £13.65 |
| 35 | 8.1 litres | £11.70 |
| 40 | 7.1 litres | £10.24 |
| 45 | 6.3 litres | £9.10 |
| 50 | 5.6 litres | £8.19 |
| 55 | 5.1 litres | £7.45 |
| 60 | 4.7 litres | £6.83 |
Comparing metric vehicle specifications
European specifications often quote L/100km. Lower L/100km means less fuel is used for a fixed distance; this calculator expresses the same consumption as a cash cost at your entered pump price.
Using the result
Change one input at a time when comparing options. MPG reflects fuel efficiency; price reflects what you pay at the pump. A low result is not automatically “good” or “poor” without comparing similar vehicle size, journey type and fuel price.
Assumptions and limitations
- UK / imperial MPG is used.
- Traffic, speed, weather, load, tyre pressure and driving style can change real MPG.
- The calculation does not include parking, maintenance or other motoring costs.
Helpful questions
Does this use UK or US MPG?
UK / imperial MPG. A UK gallon is larger than a US gallon, so the figures cannot be mixed.
Why does higher MPG lower the cost?
The same distance requires fewer litres at higher MPG.
What if my pump price changes?
Enter the price you expect to pay; cost changes directly with it.
Is this the same as cost per mile?
No. It fixes the distance at 100 km; use the per-mile calculator for a unit rate.
Will I get this exact result on the road?
No. It is based on entered MPG, which may differ from real-world conditions.
Related calculators
- Fuel Cost per 100 Miles
Calculate fuel cost and litres used for 100 miles.
- MPG to L/100km Converter
Convert UK MPG and litres per 100km.
- Petrol Cost Per Mile
Calculate petrol cost per mile.