Planning a drive? Calculate fuel cost by hand in seconds: divide your trip distance by your car's mileage (mpg or km/l), multiply by the fuel price per gallon or litre — and the free calculator below does the exact math for you, instantly, with no signup.
Quick answer: How do I calculate fuel cost for a road trip by hand? Divide your total trip distance by your car's mileage (miles per gallon or km per litre), then multiply that fuel amount by the price per gallon or litre. Example: 500 miles ÷ 25 mpg = 20 gallons × $3.50 = $70 for the trip.
Trip details
Why estimate fuel cost before a trip?
Fuel is usually the biggest variable cost of any road trip. Knowing the number in advance helps you budget accurately, compare driving against flying or public transport, and split costs fairly with fellow travellers. Fleet managers and delivery drivers use the same maths to price jobs and spot vehicles that are burning more fuel than they should.
Your real-world mileage matters more than the brochure figure. Stop-and-go city traffic, air conditioning, heavy loads and under-inflated tyres can all push consumption 10–25% above the official rating. For the most accurate estimate, use the mileage your own car achieves — many dashboards show a long-term average.
How the calculation works
The calculator divides your trip distance by your vehicle's mileage to find how much fuel you will burn, then multiplies by the fuel price. It also shows the cost per kilometre or mile, which is handy for comparing cars or deciding whether a detour is worth it.
Fuel needed = distance ÷ mileage Total cost = fuel needed × price per litre/gallon
How do I calculate fuel cost for a road trip by hand
You can calculate fuel cost for a road trip by hand in three steps — no app needed:
Divide distance by mileage. For a 500-mile trip in a car that does 25 mpg: 500 ÷ 25 = 20 gallons needed.
Multiply by fuel price. At $3.50 per gallon: 20 × $3.50 = $70 for the trip.
Metric works the same. For a 500 km trip at 15 km/l: 500 ÷ 15 = 33.3 litres × price per litre.
Round the price up a little (about 10%) to leave room for detours, traffic, and air conditioning. Then use the calculator above to get the exact figure for your real route.
Ways to cut fuel costs
Keep tyres inflated to the recommended pressure — low tyres raise consumption by up to 3%.
Drive smoothly at moderate speeds; fuel use climbs sharply above 100 km/h.
Remove roof boxes and excess weight when you do not need them.
Combine errands into one trip instead of several short cold-start drives.
Calculate fuel cost by hand
To calculate fuel cost by hand, all you need is the fuel cost formula: fuel needed = trip distance ÷ fuel efficiency (your car's mpg or km/l), then total cost = fuel needed × fuel price per gallon or litre. That gives you both the fuel you will burn and your cost per km or mile — the two numbers every trip budget needs. Enter the same three values in the free calculator above and it runs this exact math for you in metric or US units, instantly and free. Updated October 2026.
Common questions
How do I calculate fuel cost for a road trip by hand step by step?
How do I calculate fuel cost for a road trip by hand step by step? Divide your total distance by your car's mileage to find the fuel needed, then multiply by the fuel price — for example, 500 miles ÷ 25 mpg = 20 gallons × $3.50 = $70. The free calculator above does this instantly.
How do I calculate fuel cost for a road trip by hand in miles and gallons?
How do I calculate fuel cost for a road trip by hand in miles and gallons? Divide the trip miles by your car's mpg to get gallons, then multiply gallons by the price per gallon. Switch the calculator above to US units and it applies the same maths.
How is fuel cost calculated?
Fuel needed equals trip distance divided by your vehicle's mileage (e.g. 500 km ÷ 15 km/l = 33.3 litres). Total cost equals fuel needed multiplied by the fuel price per litre or gallon.
What is a good fuel mileage?
A typical petrol car delivers 12–20 km/l (28–47 mpg). Hybrids can exceed 20 km/l, while large SUVs may get under 10 km/l. Check your owner's manual or dashboard trip computer for your car's figure.
How can I reduce my fuel cost per trip?
Keep tyres properly inflated, drive at steady speeds, avoid idling, remove roof racks when unused, and plan routes to avoid traffic. Each habit can save 5–15% on fuel.
Does this work with gallons and miles?
Yes. Switch to US units to enter distance in miles, mileage in mpg and fuel price per gallon. The maths is identical; only the units change.
Is this calculator free?
Yes — 100% free, no signup, no limits. Everything runs in your browser.
How do I convert mpg to L/100km?
L/100km = 235.2 ÷ mpg — so 30 mpg ≈ 7.8 L/100km. The formulas invert because mpg measures distance per unit of fuel while L/100km measures fuel per unit of distance; one goes up when the other goes down.
Why does my car use more fuel than its official rating?
Official figures come from controlled lab cycles; real driving adds traffic, air conditioning, short trips, speed, and cargo. Expect 10–25% worse in practice — use your own measured average over a few tankfuls for accurate trip budgets.
Is it cheaper to drive fast or slow on the highway?
Slower wins: aerodynamic drag grows with the square of speed, so 120 km/h can burn 15–25% more fuel than 100 km/h. For most cars the efficiency sweet spot is 80–100 km/h in top gear — you'll arrive slightly later but measurably richer.
How much does gas cost for a 500-mile trip?
Roughly $59–$70: a 500-mile trip at 30 mpg burns about 16.7 gallons, so $58.33 at $3.50/gal. A 22 mpg SUV costs about $79.55 for the same trip. Enter your own mpg and price in the free tool above for your exact number — no signup.
Estimates only. Actual fuel use varies with driving style, traffic, load and vehicle condition.
The fuel cost formula in metric and US units
Trip fuel cost is two multiplications: fuel used = distance ÷ efficiency, then cost = fuel used × price per unit. The wrinkle is that efficiency inverts between systems — metric uses L/100km (lower is better) while the US uses mpg (higher is better) — so the formulas look different but compute the same thing.
Worked examples: a 600 km trip at 8.0 L/100km → (600 ÷ 100) × 8 = 48 litres; at $2.10/L = $100.80. In US units: 400 miles at 30 mpg → 400 ÷ 30 = 13.33 gallons; at $3.50/gal = $46.67.
Practical tips: use your real-world efficiency, not the lab figure — expect 10–25% worse with traffic, AC, and speed. Fuel economy collapses above ~100 km/h because aerodynamic drag rises with the square of speed; cruising at 90–100 km/h in top gear is the sweet spot. Limitation: the calculator covers fuel only — tolls, wear, depreciation, and price changes along the route are on you.
Cost per kilometer — the number that compares everything: divide trip cost by distance to get your true driving cost: our 600 km / $100.80 example = $0.168/km in fuel alone. Add ownership costs (depreciation, insurance, maintenance — typically $0.20–0.40/km more) and most "cheap" drives aren't cheap at all, which is the honest math behind fly-vs-drive decisions. For EV comparisons, the same formula works in kWh: consumption (kWh/100km) × electricity price. A car using 16 kWh/100km at $0.15/kWh costs $0.024/km — roughly one-seventh the fuel cost of our petrol example — though purchase price and charging time are the real EV trade-offs. Hybrids shine in city driving (regenerative braking recovers stop-start energy) but offer little highway advantage, so match the technology to your driving mix. Whatever you drive, the calculator's per-km figure is the unit that makes honest comparisons possible.