Math

Fuel Cost Calculator

Quick answer: how much will this trip actually cost in gas? Or maybe the bigger question — how much is your daily commute costing you per month, total? People underestimate this all the time. A 40-mile round-trip commute in a 25 MPG car at $3.50/gal costs $112/month in gas alone, before parking, tolls, or wear and tear. This calculator runs the math for any trip distance + MPG + gas price, and if you give it a monthly day count it'll add up the full monthly cost. Useful for trip budgeting, commute decisions, vehicle comparisons, and the occasional reality check on driving costs.

Enter distance, MPG, and gas price.

The simple formula

Gas cost = (distance ÷ MPG) × price per gallon. That's it.

Worked example: 400-mile road trip in a 28-MPG car at $3.50/gal. Gallons = 400 / 28 = 14.3. Cost = 14.3 × $3.50 = $50. Round trip = $100. For a commute use case: 40-mile round trip × 20 work days = 800 miles/month. Gas cost = 800 / 28 × $3.50 = $100/month, just for gas.

Real cost-per-mile (what the calculator does NOT include)

Gas is only part of driving cost. AAA's 2024 "Your Driving Costs" puts total cost per mile at:

Small sedan: $0.60/mile
Mid-size sedan: $0.74/mile
SUV: $0.85/mile
Pickup truck: $0.93/mile
EV: $0.65/mile (more depreciation, less fuel/maintenance)

Components: depreciation (40% of total cost), insurance (15-20%), fuel (15-20%), maintenance + repairs (10-15%), license/registration (3-5%). Gas-only math vastly understates real driving cost. For a quick rule, 2-3x the gas-only cost approximates total cost per mile in most vehicles.

Worked example: 50-mile round-trip commute in a sedan. Gas at 28 MPG, $3.50/gal = $6.25/day. Total cost using AAA's $0.74/mile = $37/day. The gas portion is only 17% of total driving cost.

How to use this calculator

Distance: one-way distance in miles.
MPG: your actual measured MPG (track 3-4 fill-ups: miles driven ÷ gallons added), not the EPA sticker.
Gas price ($/gal): current pump price.
Round-trip days per month: for commute calculations.
Output: one-way cost, gallons used, round-trip cost, monthly cost.
For total driving cost, double or triple the gas-only number to account for depreciation, insurance, and maintenance.

Common scenarios

Daily commute 40 miles round trip, 28 MPG sedan, $3.50/gal, 22 work days. One-way $2.50. Round trip $5. Monthly $110. Add insurance + depreciation + wear: real cost closer to $250-350/month.

Road trip 800 miles one-way (1,600 round), 25-MPG SUV, $3.75/gal. One-way gallons 32 = $120. Round trip $240. Plus food + hotels + miscellaneous = full trip cost $500-800. Cheaper than flying for a family of 4 if you have time.

Pickup truck 18 MPG, $3.50/gal, 25-mile commute, 20 days/month. One-way $4.86. Monthly $194. Real total cost on a pickup at AAA's $0.93/mile: $930/month — the cost of a small car payment, just to commute.

FAQ

Should I use EPA MPG or actual MPG? +

Actual. EPA values are lab tests that miss real-world conditions: highway speed (often higher than EPA), city stop-and-go intensity, weather, cargo, driving style. Most drivers achieve 5-15% below EPA combined. Track 3-5 consecutive fill-ups, compute your real MPG, use that.

How do I save on gas? +

Drive slower (60 vs 75 mph = ~15% better MPG), use cruise control on highway, accelerate gently, coast to stops instead of braking late, keep tires properly inflated (5 PSI low = 1-2% MPG loss), declutter the trunk (extra weight = MPG hit). Smaller cars and hybrids matter more than driving tricks though.

What's a good MPG? +

Hybrid sedan: 45-55 MPG. Compact gas sedan: 30-40 MPG. Mid-size sedan: 25-30 MPG. SUV: 20-25 MPG. Pickup truck: 15-22 MPG. EV: 100-130 MPGe (electricity equivalent). For pure dollar cost per mile, EVs at home charging cost roughly $0.04-0.07/mile vs $0.10-0.20/mile for gas.

How do EV charging costs compare? +

Home charging at $0.13/kWh + 3.5 mi/kWh efficiency = $0.037/mile. Public DC fast charging at $0.35-0.50/kWh = $0.10-0.14/mile (comparable to a gas car). Most EV owners charge 90%+ at home; the public-charging cost only matters for road trips.

Should I include diesel or premium gas premium? +

Diesel typically costs 10-20% more than regular gas but diesel engines get 20-30% better MPG — net cost per mile is similar or slightly better. Premium-required cars (most performance and luxury) cost 15-20% more per gallon than regular. If you can use regular safely (check owner's manual), do so.

Is it cheaper to drive or fly? +

For solo or couples: usually fly for distances over 600 miles when factoring time. For families of 3+ on a 1,000-mile trip: driving's gas cost ($150-300) plus modest hotels often beats four plane tickets ($1,200+). Add EV (free fast charging) and the math swings further toward driving.

What about working from home (WFH) savings? +

Two days/week WFH on a 50-mile round-trip commute saves ~$70-100/month in gas alone, $200-350/month in full driving cost. Over a year, $2,400-4,200. WFH also avoids parking ($100-300/month in many cities) and lunch out ($100-200/month). Significant household cash flow improvement.

How accurate is the pump's MPG / fuel economy display? +

Most car onboard displays are within ±5% of actual MPG. Some over-report by 5-10% (manufacturers tune toward optimistic). The most accurate method remains: trip odometer ÷ gallons added at fillup, averaged over 3-5 fillups.