How do I calculate fuel costs for a journey?

Divide the journey distance by your car's fuel efficiency (miles per gallon or miles per litre), then multiply by the current fuel price per litre or gallon. For example, a 100-mile trip at 40 MPG with fuel at £1.40/litre: 100 ÷ 40 = 2.5 gallons × 4.546 litres × £1.40 = £15.91.

What is the HMRC mileage rate?

The approved HMRC mileage rate for cars is 45p per mile for the first 10,000 business miles and 25p per mile thereafter. Motorcycles are 24p per mile and bicycles are 20p per mile.

Fuel Cost Calculator

Calculate the fuel cost of any journey based on distance, fuel price and your vehicle's MPG or L/100km.

Last updated: April 2026 · Source: HMRC — Mileage and fuel allowances

Distance

Fuel Price (pence per litre)

p/litre

Fuel Efficiency

Fuel Cost

£15.34

Litres Needed

11.4L

Cost per Mile

15.3p

Distance

100 mi

Disclaimer

This calculator is provided for informational purposes only and should not be considered as financial or tax advice. All calculations are performed locally in your browser — no personal data is collected or sent to our servers. Rates and thresholds are sourced from HMRC and GOV.UK and are updated for the current tax year. Always verify results with HMRC or consult a qualified professional before making financial decisions.

How It Works

Fuel cost is calculated by dividing the journey distance by your vehicle's fuel efficiency, then multiplying by the price per litre. UK fuel efficiency is commonly quoted in miles per gallon (MPG) but fuel is sold in litres, so a conversion is needed: 1 UK gallon = 4.546 litres.

The HMRC approved mileage allowance for business use is 45p per mile for the first 10,000 miles and 25p per mile thereafter. This is designed to cover fuel, insurance, depreciation and wear — not just fuel costs. If your employer pays less than these rates, you can claim tax relief on the difference.

This calculator lets you enter distance, fuel efficiency and fuel price to estimate the cost of any journey. It also shows the equivalent HMRC mileage allowance for comparison.

Example: 200-mile round trip, 40 MPG, fuel at £1.40/litre

Fuel needed: 200 ÷ 40 = 5 gallons = 22.73 litres
Fuel cost: 22.73 × £1.40 = £31.82
HMRC mileage: 200 × 45p = £90.00
Difference (covers wear, insurance etc.): £58.18

Source: HMRC — Mileage and fuel allowances

Frequently Asked Questions

How do I calculate fuel costs for a journey?: Divide the journey distance by your car's fuel efficiency (miles per gallon or miles per litre), then multiply by the current fuel price per litre or gallon. For example, a 100-mile trip at 40 MPG with fuel at £1.40/litre: 100 ÷ 40 = 2.5 gallons × 4.546 litres × £1.40 = £15.91.
What is the HMRC mileage rate?: The approved HMRC mileage rate for cars is 45p per mile for the first 10,000 business miles and 25p per mile thereafter. Motorcycles are 24p per mile and bicycles are 20p per mile.