Rex says
Everyday utility math — the kind you'd otherwise pull up four browser tabs for. I keep it to one clean answer.
Try a scenario
Click to load — tweak from there.Inputs
Result
Total fuel cost
$50.00
Gallons needed
14.3
Total distance
400
Psst — share this and help Rex grow
One click, a permanent link with your numbers baked in.
How to use this
- 1Enter trip distance (one-way) (mi).
- 2Enter trip type.
- 3Enter vehicle fuel economy (mpg).
- 4Enter gas price ($/gal).
- 5Read your total fuel cost on the right — it updates as you type.
- 6Hit Share to keep the scenario or send it to someone.
About this calculator
Trip fuel usage and cost are calculated from distance divided by your vehicle's miles-per-gallon rating, then multiplied by the local gas price. This calculator gives gallons needed and total fuel cost for one-way or round trips.
Worked example
Using the values the calculator loads with:
Inputs
- Trip distance (one-way): 400 mi
- Trip type: One-way
- Vehicle fuel economy: 28 mpg
- Gas price: 3.5 $/gal
Results
- Total fuel cost: $50.00
- Gallons needed: 14.3
- Total distance: 400
What each field means
Inputs
- Trip distance (one-way) (mi)
- The trip distance (one-way) used in the calculation, measured in mi. Starts at 400 mi so you have a working example on load.
- Trip type
- Pick the option that matches your situation — the maths changes per option. Choices: One-way, Round trip.
- Vehicle fuel economy (mpg)
- The vehicle fuel economy used in the calculation, measured in mpg. Starts at 28 mpg so you have a working example on load. Accepted range: 5–100 mpg.
- Gas price ($/gal)
- The gas price used in the calculation, measured in $/gal. Starts at 3.5 $/gal so you have a working example on load. Accepted range: 1–8 $/gal.
Results
- Total fuel cost
- Returned as a money amount in US dollars and shown as the headline result. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- Gallons needed
- Returned as a decimal number. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- Total distance
- Returned as a whole number. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
FAQ
How much gas will my trip use?
A 400-mile one-way trip at 28 mpg uses about 14.3 gallons; at $3.50/gallon, that's roughly $50 in fuel cost — double both for a round trip.
Does highway vs city driving change the mpg to use?
Yes — use your car's highway mpg rating for long road trips since highway driving is typically 15-25% more fuel-efficient than the combined or city rating.
How does towing or cargo weight affect trip cost?
Towing a trailer or carrying heavy cargo can cut fuel economy by 20-40%, so if you're towing, use a reduced mpg estimate to avoid underbudgeting your trip fuel cost significantly.
Should I add a buffer to the estimate?
Adding 10% covers detours, traffic idling, and AC use, which all reduce real-world mpg below the vehicle's rated average.
Accuracy and limitations
- Estimates assume standard, average conditions — local rules, pricing, and materials vary.
- Results are rounded for readability; add a buffer before ordering, booking, or committing.
- Double-check anything with a real cost attached against a local quote.
Related tools
Cite this calculator
Writing about this topic? Grab a citation — every link helps keep these tools free.
RevenueLab. (2026). How Much Gas Will My Trip Use?. Retrieved from https://www.revenuelab.fyi/toolbox/how-much-gas-will-my-trip-use
<p>Source: <a href="https://www.revenuelab.fyi/toolbox/how-much-gas-will-my-trip-use" target="_blank" rel="noopener">How Much Gas Will My Trip Use? — RevenueLab</a> (2026).</p>
Source: [How Much Gas Will My Trip Use? — RevenueLab](https://www.revenuelab.fyi/toolbox/how-much-gas-will-my-trip-use) (2026).