- How is the fuel cost calculated?
- For imperial inputs: fuel_used = distance ÷ MPG, then fuel_subtotal = fuel_used × price_per_gallon. A 600-mile round trip in a 28-MPG sedan needs 21.43 gallons; at $3.50/gal that's $75. For metric inputs: fuel_used = distance × (L/100km) ÷ 100, then × price_per_liter. A 1,000-km drive in a car rated 8 L/100km uses 80 liters; at €1.70/L that's €136. Hybrid drivers should use their real-world combined MPG (often 5-10% lower than the EPA sticker on highway-heavy trips, where the gas engine runs more); EV drivers should use a tool built for kWh instead.
- Why does the tool bill (days − 1) nights of lodging, not full days?
- Because a 3-day trip (Mon–Wed) only needs 2 sleep nights — Mon-to-Tue and Tue-to-Wed. Wednesday night you're home. A weekend (Sat–Sun) needs 1 night. A week (7 days) needs 6 nights. The heuristic covers ~90% of trips. The edge cases: (a) you book a hotel the night BEFORE departure to get an early start, (b) you do an overnight drive home, (c) you take a red-eye flight back. For those, the engine's lodging_nights field lets you override — set it explicitly to the actual number of paid nights. Day trips (1 day) bill zero lodging by definition.
- How accurate is this for budgeting a real trip?
- Accurate to about ±10% if your inputs are realistic. The biggest sources of drift: (1) gas prices move daily — use today's price, not last month's; (2) fuel economy degrades 5-10% in mountain terrain, headwinds, hot weather (AC running), and city stop-and-go; (3) food costs vary hugely by region — $25/day works in rural America, $75/day is closer in NYC or San Francisco; (4) lodging spikes during peak season and holiday weekends. Build in a 10-15% buffer for unexpected costs (souvenirs, an extra restaurant meal, a parking ticket) and you'll usually land close.
- What's a realistic budget for food per person per day on a road trip?
- US 2025 averages — modest: $25-35/day (gas station coffee, fast food, one sit-down meal); mid-range: $40-60/day (sit-down lunch + dinner, coffee shops); generous: $70-100/day (nicer restaurants, drinks, dessert). Europe runs a bit lower in casual dining (€20-30 mid-range) but pricier in tourist zones. Two cost-cutters that actually work on road trips: pack a cooler with sandwich fixings (cuts $15-25/day for the group), and have one big restaurant meal at lunch (when entree prices are 30-40% lower than dinner) and a light/grocery dinner.
- Should I include the cost of getting my car serviced before the trip?
- For a long trip, yes — fold it into attractions or as an extra line. Pre-trip oil change + tire check is $80-150 on a normal car; if the trip is over 1,500 miles you should pad it in. Don't include depreciation as a cost line — it'll bias the number toward 'never drive anywhere again,' which isn't the right framing. The IRS standard mileage rate (~$0.67/mile in 2025) is intended for tax deductions on business driving and bundles depreciation + insurance + maintenance into a single per-mile number; using that figure for a vacation budget will roughly double the cost of any real trip.
- How does this compare to flying for the same distance?
- Driving wins decisively up to ~400 miles round trip — even with lodging, you'll usually beat the all-in flight cost (tickets + checked bags + airport parking + rental car at the destination + Uber to/from your home airport). Between 400-1,200 miles it's a toss-up that depends on the group size: 1 person flying often beats 1 person driving past 800 miles; 4 people sharing a car beats 4 plane tickets up to ~1,500 miles. Past 1,500 miles flying almost always wins on TOTAL cost, but driving still wins on flexibility (no checked-bag fees, you've got a car at the destination, you control the schedule).
- What if I'm renting a car instead of using my own?
- Use the rental's official MPG (the rental site lists it), and add the daily rental rate × duration_days to attractions or as an extra mental line. A typical US economy rental runs $40-70/day plus optional insurance ($15-30/day); a midsize SUV runs $60-100/day. Don't forget the airport surcharge (10-15% on most rentals from the airport, vs. picking up at a city location) and the underage-driver fee if anyone in the group is under 25 ($20-30/day per driver). Fuel-economy-wise, rentals are usually rated honestly because rental companies disclose actual fleet averages.
- How do I split costs fairly when not everyone drove?
- The simplest fair split: divide total_cost evenly across all travelers (what this tool returns as per_person). If one person did all the driving, the group sometimes tips the driver an extra $30-50 — not a fuel reimbursement but a thank-you for the labor. If one person used their own car (vs. a rental), add the IRS rate × distance to their contribution credit ($0.21/mile non-business rate is fairer than the full $0.67 — it covers fuel + a fair share of wear). Splitwise and similar apps handle the bookkeeping; for a trip with 3+ travelers and more than ~5 shared expenses, they save the awkward 'who paid what' email thread at the end.
