Petrol Consumption Calculator
Enter your trip details to calculate fuel economy in L/100 km, km/L, and estimated fuel cost.
Why petrol consumption matters
Knowing how to calculate petrol consumption helps you control two things: your driving costs and your car’s efficiency. If your numbers suddenly get worse, it can be an early warning sign of low tyre pressure, poor driving habits, traffic-heavy routes, or maintenance issues.
It also helps when comparing vehicles. A car that uses less fuel per 100 km may save you a substantial amount over a year, especially if you commute daily or travel long distances.
The basic formula
Petrol consumption is usually expressed in litres per 100 kilometres (L/100 km).
Lower L/100 km means better fuel efficiency. For example, 5.8 L/100 km is more efficient than 8.9 L/100 km.
Related formulas
- km/L = Distance (km) ÷ Litres used
- Total trip fuel cost = Litres used × Price per litre
- Cost per 100 km = (L/100 km) × Price per litre
Step-by-step method (manual calculation)
1) Fill your tank
Start from a full tank and reset your trip meter to zero.
2) Drive normally
Use the car as you usually do. The longer the distance, the more reliable your result.
3) Refill to full tank again
At your next fill-up, record:
- Distance from the trip meter (in km)
- Litres needed to refill (this equals fuel consumed)
4) Apply the formula
Example:
- Distance = 515 km
- Fuel used = 39.2 L
L/100 km = (39.2 ÷ 515) × 100 = 7.61 L/100 km
km/L = 515 ÷ 39.2 = 13.14 km/L
Quick reference table
| Fuel Economy | Interpretation | Typical Usage |
|---|---|---|
| 4.5–6.0 L/100 km | Very efficient | Small hybrids, compact cars |
| 6.1–8.0 L/100 km | Good/average | Most small to mid-size cars |
| 8.1–11.0 L/100 km | Higher consumption | Larger sedans, SUVs, city driving |
| 11+ L/100 km | Heavy consumption | Performance cars, towing, stop-start traffic |
How to get accurate results
- Use the full-tank method instead of relying only on dashboard estimates.
- Measure over multiple fill-ups and average the results.
- Keep tyre pressure correct; under-inflated tyres increase fuel use.
- Avoid aggressive acceleration and high-speed cruising when possible.
- Reduce extra weight in the boot and remove roof racks if not needed.
Common mistakes to avoid
- Mixing units (miles with litres, or km with gallons).
- Forgetting to reset the trip meter.
- Using one very short trip as your final result.
- Not refilling to the same level each time.
Petrol consumption vs. fuel cost
Fuel economy tells you how efficiently your vehicle uses fuel, but cost also depends on local petrol prices. Two drivers can have the same 7.5 L/100 km but different monthly costs if one pays more per litre or drives more kilometres.
That’s why combining consumption and fuel price gives the most practical number: cost per 100 km.
Final thoughts
If you can calculate petrol consumption, you can make better decisions about driving style, route planning, maintenance, and even whether it’s time to switch vehicles. Use the calculator above regularly and track your trend month by month. Small improvements in L/100 km can lead to big savings over time.