How do I work out my monthly fuel cost?

Divide the miles you drive in a month by the mpg to get gallons, then multiply by the price per gallon. 1,000 miles at 30 mpg is 33.333 gallons, and at 3.50 a gallon that is 116.67. The working under the answer writes out each step, including any unit conversion.

How are the weekly and yearly figures worked out?

A year is 12 months of driving, so 1,000 miles a month is 12,000 miles a year, which costs 1,400.00. A week is the year times 7, divided by the 365.25 days of an average year, which gives 26.83. A month is a little over four weeks, so the weekly figure is not the monthly one divided by 4.

What if I only know my daily commute?

Multiply the round trip by the days you drive in a month and enter that as the distance. A 30 mile round trip on 21 working days is 630 miles a month.

Can I split it with people I carpool with?

Yes. Set the number of people sharing and the Per person row shows each share of the monthly cost. Switch on Second vehicle to see what another car would cost for the same monthly distance.

Monthly Fuel Cost Calculator

Enter how far you drive in a month, the vehicle's fuel economy and the price you pay, and the page returns the monthly fuel cost with the weekly and yearly figures beside it. It opens on 1,000 miles a month at 30 mpg and 3.50 a gallon, which is 116.67 a month. Each field takes miles or km, mpg, UK mpg, L/100km or km/L, and a price per gallon or per litre.

Monthly fuel cost116.6733.333 US gal over 1,000 miles a month

Distance a month

Efficiency

Measured in

Fuel price

Quoted

Sharing

Compare

Second vehicle

Enter the price in whatever currency you buy fuel in. The answer comes back in the same one, because the arithmetic never touches an exchange rate.

Fuel neededa month
33.333 US gal (126.18 L)
Per weeka year × 7 ÷ 365.25 days
26.83
Per monthfuel only, the distance you entered
116.67
Per yeara month × 12
1,400.00
Per persona month, one person
116.67
Per mile and per kmthe same money over two rulers
0.1167 per mile, 0.0725 per km
The workingevery conversion, in full
1,000 mi ÷ 30 mpg = 33.333333 US gal; 33.333333 US gal × 3.50 = 116.67; 116.6667 × 12 = 1,400.00 a year; 1,400.00 × 7 ÷ 365.25 = 26.83 a week

Two gallons, and one unit that runs backwards. Choose the gallon used by your fuel price and efficiency figure. L/100km measures fuel per distance, so a lower number means less fuel used, and it multiplies where mpg divides. Every conversion the answer needs is written into the working above with the constant it used, so you can check which gallon went where.

Common questions

How do I work out my monthly fuel cost?: Divide the miles you drive in a month by the mpg to get gallons, then multiply by the price per gallon. 1,000 miles at 30 mpg is 33.333 gallons, and at 3.50 a gallon that is 116.67. The working under the answer writes out each step, including any unit conversion.
How are the weekly and yearly figures worked out?: A year is 12 months of driving, so 1,000 miles a month is 12,000 miles a year, which costs 1,400.00. A week is the year times 7, divided by the 365.25 days of an average year, which gives 26.83. A month is a little over four weeks, so the weekly figure is not the monthly one divided by 4.
What if I only know my daily commute?: Multiply the round trip by the days you drive in a month and enter that as the distance. A 30 mile round trip on 21 working days is 630 miles a month.
Can I split it with people I carpool with?: Yes. Set the number of people sharing and the Per person row shows each share of the monthly cost. Switch on Second vehicle to see what another car would cost for the same monthly distance.

Exact arithmetic on the numbers entered: distance divided by efficiency, times price. Real consumption varies with speed, load and weather, so treat the result as the figure your own inputs imply.