Fuel Cost Calculator Ireland

Fuel cost per kilometre: quick examples

To estimate petrol or diesel running cost, multiply distance (km) × litres per 100 km ÷ 100 × pump price per litre. These illustrative examples use €1.80 per litre; enter today’s actual fuel price in the calculator above.

At 6.5 L/100 km and €1.80/L, petrol alone costs about 11.7 cent per kilometre, excluding tax, tyres, depreciation, repairs and insurance. If comparing a petrol or diesel car with an electric car, calculate the other side using the EV Charging Cost Calculator; for home charging with planned solar panels, explore the Compound Solar Hub.

What this calculator is for

This calculator converts distance, vehicle fuel consumption and fuel price into trip or annual fuel cost. It is useful for commuting comparisons, mileage budgeting and comparing conventional vehicles.

How to read the result

Fuel economy and price are equally important. A car that uses 20% less fuel reduces consumption cost by roughly 20% at the same fuel price, but real-world efficiency can vary with speed, temperature, traffic and driving style.

Worked example

A petrol car using 6.5 L/100 km over 15,000 km consumes about 975 litres. At €1.80 per litre, that is about €1,755 a year before tax, servicing, tyres, insurance or depreciation.

Irish context

SEAI publishes fuel-cost comparisons using periodically updated Irish fuel prices and notes that actual results vary with driving cycles, behaviour, weather and vehicle condition. Fuel is only one part of total motoring cost.

What can change the answer

Mileage, urban/motorway mix, load, tyre pressure, weather and fuel price can move the result. Hybrid vehicles can perform very differently depending on the journey type.

Common mistakes to avoid

Do not compare two cars on fuel alone. Depreciation, finance, insurance, tax and servicing can outweigh fuel differences. And use your own real consumption where possible rather than brochure figures.

Related Compound tools

Use the EV Charging Cost Calculator for electric driving and the Car Finance Calculator for acquisition financing. If you are deciding which drivetrain to buy rather than calculating fuel alone, use EV vs Petrol vs Diesel in Ireland to compare total ownership factors.

Frequently asked questions

Is L/100 km better when lower?

Yes.

Does this include motor tax?

No.

Can I use mpg?

Use the calculator’s supported units or convert consistently.

Why does my real cost differ from the rated consumption?

Driving conditions and behaviour vary from test cycles.

Fuel is only one part of the cost of driving

Fuel is highly visible because you pay for it repeatedly, but it is often not the largest ownership cost. Depreciation, finance interest, insurance, servicing, tyres, motor tax and repairs can materially exceed the difference between two cars’ fuel bills.

That matters when deciding whether to replace a car with a more efficient one. Saving €400 a year in fuel does not automatically justify spending €15,000 more on the replacement vehicle.

A better comparison is total cost of ownership over the period you expect to keep the car. Use this calculator to isolate fuel, then add the other costs separately.

Driving style also has a real effect. Repeated short cold journeys, heavy acceleration, roof boxes, low tyre pressure and high motorway speeds can all push real consumption above the figure used in the calculator. If you already own the car, use fuel receipts and distance travelled over several tanks to estimate your own L/100 km rather than relying only on the manufacturer’s test figure.

Advanced mode: turn trip economics into an annual fuel budget

Advanced mode adds annual distance while keeping the same L/100 km and pump-price assumptions used for the trip calculation. That produces an annual fuel-volume and fuel-cost estimate without requiring you to guess how many identical trips you make.

For example, 15,000 km a year at 6.5 L/100 km requires about 975 litres. The euro result then changes directly with the fuel price entered.

This is deliberately a fuel-only annual budget. It is not total cost of ownership. A cheaper-to-fuel vehicle can still be more expensive overall once depreciation, finance, insurance, tax, servicing and the purchase-price difference are included.

Use real consumption, not brochure consumption, where possible

Official or advertised fuel-consumption figures are useful for comparing cars on a consistent basis, but your personal fuel budget is driven by what the vehicle actually achieves in your driving.

Short trips, cold starts, motorway speed, heavy traffic, roof boxes, towing, tyre pressure and driving style can all move real-world litres per 100 km away from a rated figure.

If you already own the car, a strong input is the average consumption shown over several full tanks rather than the best single journey displayed on the dashboard.

Convert fuel economy into a decision metric

Fuel cost becomes more useful when expressed in three ways:

• cost per 100 km,
• annual fuel spend,
• and the difference between two vehicles.

For example, a car saving 1.5 L/100 km can sound significant, but whether it matters financially depends on annual distance and fuel price. At low mileage the euro saving may be modest; at high mileage it can become material.

Advanced mode turns that efficiency difference into an annual budget so you can compare it with the extra purchase price of the more efficient vehicle.

Stress-test fuel price

Do not build a five-year ownership decision around today’s pump price as though it were fixed.

Run a low, central and high fuel-price scenario. If one car only justifies its higher purchase price when fuel prices are unusually high, the economics are fragile. If it remains attractive across a wide range, the decision is more robust.

Diesel, petrol and hybrid comparisons need more than L/100 km

A lower fuel bill does not automatically mean lower total ownership cost. A diesel or hybrid may differ in purchase price, depreciation, maintenance, motor tax, insurance or financing.

Use this calculator to isolate the fuel component, then move the result into the Lifetime Cost Calculator for the ownership decision.

If the alternative is an EV, use the EV Charging Cost Calculator so both options are compared on annual driving distance rather than on incompatible units such as litres and kWh.

Separate sunk cost from future cost

If you already own a reliable car, the relevant question is usually not “which car is cheapest from new?” but “does the future fuel saving justify the cost of changing from the car I already have?”

That means comparing the additional capital cost of changing vehicle with the annual fuel saving and other ownership differences. A more efficient replacement can be a good car and still be a poor financial swap if the fuel saving is too small relative to the cash required to change.

Method and limitations

The tool converts distance and fuel consumption into litres used, then multiplies by the entered fuel price. It does not model depreciation, maintenance, insurance or tax.

Useful sources

• SEAI — Journey cost calculator

The replacement-car trap

Lower fuel use does not automatically justify changing cars.

Suppose a newer car saves €500 a year in fuel but costs €12,000 more after selling your current car. Ignoring finance, depreciation and maintenance differences, fuel savings alone would take 24 years to recover that price gap.

That does not mean the newer car is a bad purchase. It means fuel economy should be separated from the broader ownership decision.

If you are comparing petrol, diesel, hybrid and EV options, calculate fuel/charging first, then add finance, insurance, motor tax, servicing, expected depreciation and how long you actually plan to own the vehicle.

The biggest cost in motoring is often not the one shown at the pump.