Fuel Cost Calculator
Trip fuel cost from distance, economy and price.
Reviewed by the Calculation Machine team · Updated 24 October 2026 · How we check our maths
Your values
ⓘ Live results
- Total fuel cost
- $45.28
- Fuel needed
- 13.13 gallons
- Cost per person
- $45.28
- Cost per mile
- $0.108
- Round trip
- $90.56
Quick answer
Trip fuel cost is the distance divided by your fuel economy, multiplied by the fuel price: cost = miles ÷ mpg × price per gallon. A 420-mile drive in a car that gets 32 mpg uses 13.13 gallons; at $3.45 a gallon that costs $45.28, or about 10.8 cents per mile.
What the Fuel Cost calculator does
This calculator works out how much fuel a journey needs and what it will cost, then splits the total between passengers and doubles it for a round trip. It also gives cost per mile, which is handy for comparing cars, pricing mileage reimbursement against actual fuel spend, or budgeting a commute.
It works for any vehicle where you know miles per gallon – cars, trucks, motorhomes, motorcycles and boats. Use your real-world mpg rather than the EPA sticker figure if you can; highway driving at 75 mph, a roof box, towing or a full load can cut economy by 10–30%. The MPG calculator finds your actual figure from a fill-up.
The result covers fuel only. For a full trip budget including tolls, parking and lodging, use the road trip cost calculator; to compare with an electric car, see the EV vs gas cost calculator.
The formula
Fuel needed (gal) = distance ÷ mpg Cost = fuel needed × price per gallon Cost per person = cost ÷ people Cost per mile = price ÷ mpg
| Symbol | Meaning | Unit |
|---|---|---|
| distance | One-way trip distance | miles |
| mpg | Fuel economy for this kind of driving | miles per US gallon |
| price | Fuel price at the pump | $ per US gallon |
| people | Number of people sharing the cost | count |
This is straightforward unit arithmetic. It assumes US gallons (3.785 L). For UK mpg, which uses the 4.546 L imperial gallon, either enter UK mpg with the price per imperial gallon, or convert UK mpg to US mpg by multiplying by 0.833. To use L/100 km, convert first: US mpg = 235.2 ÷ L/100 km – the MPG to L/100km converter does this.
Worked examples
Family road trip split four ways
Four friends drive 1,150 miles one way in an SUV averaging 24 mpg, with gas at $3.29.
Inputs
- Trip distance1150 miles
- Fuel economy24 mpg
- Fuel price3.29 $/gal
- Split between4 people
Result
- Total fuel cost$157.65
- Fuel needed47.92 gallons
- Cost per person$39.41
- Cost per mile$0.137
- Round trip$315.29
About 48 gallons and $158 each way, or $39.41 per person. The round trip is about $315 – budget a little extra for detours and idling in traffic.
Daily commute cost
A 30-mile round-trip commute in a sedan that gets 28 mpg, with gas at $3.60.
Inputs
- Trip distance30 miles
- Fuel economy28 mpg
- Fuel price3.6 $/gal
- Split between1 people
Result
- Total fuel cost$3.86
- Fuel needed1.07 gallons
- Cost per person$3.86
- Cost per mile$0.129
- Round trip$7.71
$3.86 a day, roughly $85 a month over 22 working days. At 12.9 cents per mile, fuel is well below the full per-mile cost of owning a car once depreciation, insurance and maintenance are added.
Boat outing
Three people take a 60-mile run in a boat burning 10 gallons an hour at 30 mph – 3 mpg – with marina fuel at $4.80.
Inputs
- Trip distance60 miles
- Fuel economy3 mpg
- Fuel price4.80 $/gal
- Split between3 people
Result
- Total fuel cost$96
- Fuel needed20 gallons
- Cost per person$32
- Cost per mile$1.6
- Round trip$192
20 gallons and $96, or $32 each. Boat economy changes sharply with speed and load, so use the engine maker's fuel curve at your cruising rpm.
Boats: converting gallons per hour to mpg
Boat engines are rated in gallons per hour (GPH), not miles per gallon. Convert with mpg = speed (mph) ÷ GPH. Use knots and nautical miles together if you prefer: nautical mpg = knots ÷ GPH. Fuel burn rises steeply above planing speed, so slowing by a few mph can cut fuel use significantly. Keep at least a third of your fuel in reserve for the return leg and for headwinds or current – the common "rule of thirds" for boaters.
Driving time for a road trip
Driving time is distance ÷ average speed. Highway trips usually average 55–65 mph including slowdowns, so 1,150 miles is roughly 18–21 hours behind the wheel before stops. Add 15–30 minutes for every 2–3 hours of driving for fuel, food and rest breaks. A tank range check helps plan stops: tank size × mpg gives miles per tank – a 16-gallon tank at 24 mpg covers about 384 miles.
What changes your real fuel cost
Sticker mpg is measured on a standard test cycle, so real trips often come in lower. Run the calculator with a pessimistic mpg as well as your usual figure to get a cost range.
| Factor | Typical effect |
|---|---|
| Sustained speeds above about 50–60 mph | Economy falls steadily as aerodynamic drag rises with speed |
| Aggressive driving (speeding, hard acceleration and braking) | Can lower highway mpg by roughly 15–30%, per fueleconomy.gov |
| Roof-top cargo box or bikes on the roof | Noticeable loss at highway speed; a hitch-mounted carrier costs far less |
| Towing or a heavy load | Large drop that depends on trailer weight and frontal area |
| Cold weather and short trips | Lower economy until the engine reaches operating temperature |
How to use the Fuel Cost Calculator
- 1Enter the one-way distance in miles from a map app.
- 2Enter your vehicle's real-world mpg for this type of driving (highway, city or towing).
- 3Enter the fuel price per gallon you expect to pay along the route.
- 4Enter how many people are sharing, then read the total, per-person and round-trip cost.
Frequently asked questions
How do I calculate gas cost for a trip?
Divide the trip miles by your car's mpg to get gallons, then multiply by the price per gallon. 300 miles at 25 mpg is 12 gallons; at $3.50 that is $42.
How much does it cost to drive 100 miles?
Divide 100 by your mpg and multiply by the gas price. At 30 mpg and $3.50 a gallon, 100 miles costs about $11.67 in fuel.
How do I calculate fuel cost per mile?
Divide the price per gallon by your mpg. At $3.45 and 32 mpg, fuel costs about 10.8 cents a mile.
Is the IRS mileage rate the same as fuel cost?
No. The IRS standard mileage rate also covers depreciation, insurance, maintenance and repairs, so it is several times the fuel cost per mile for most cars. The rate is set each year on irs.gov.
How do I split gas money fairly on a road trip?
Split the fuel cost equally among everyone in the car, including the driver, unless you agree otherwise. Some groups also add a per-mile amount for the driver's wear and tear.
References
- Driving More Efficiently (fueleconomy.gov) — US Department of Energy and US Environmental Protection Agency
About this calculator
- Built and reviewed by the Calculation Machine team · How we build and test calculators
- Last reviewed: October 24, 2026
- Report an error