Trip fuel cost estimator

How trip fuel cost is computed from distance, economy, and price

Fuel volume for a journey equals distance divided by fuel economy when economy is written as distance per unit of fuel. A three-hundred-mile trip in a vehicle rated at thirty miles per gallon needs ten gallons; at three dollars and fifty cents per gallon the fuel cost is thirty-five dollars. The same identity works in metric: two hundred kilometres at ten kilometres per litre needs twenty litres, times the litre price. Keep units coherent—do not mix miles with kilometres per litre without converting first. Send required fields distance, fuel_economy, and fuel_price as JSON numbers or numeric strings. Aliases miles, km, trip_distance, and d map to distance; economy, mpg, km_per_l, efficiency, and fuel_efficiency map to fuel_economy; price, price_per_unit, gas_price, and fuel_unit_price map to the unit price. Non-positive distance and non-positive fuel_economy are hard errors under the product contract because they would divide by zero or invent a negative tank fill. Negative fuel_price is likewise rejected. Magnitude caps keep results finite on the Worker isolate. Identical inputs always produce identical JSON: pure arithmetic, no network, no random seed, and no wall clock.

Reading the response fields and choosing realistic inputs

The formula field is safe to show next to the numbers so users see fuel equals distance over economy and cost equals fuel times price. Prefer real-world average economy over optimistic brochure figures when the road includes hills, cold starts, or highway speeds. On success the response echoes distance, fuel_economy, and fuel_price after stable rounding, plus fuel_needed, fuel_cost, a human-readable formula string, and method equal to distance_over_economy_times_price. Use fuel_needed when you care about tank capacity, range anxiety, or how many stops you need; use fuel_cost when budgeting a holiday drive, reimbursing mileage for fuel only, or comparing cars at a stated pump price. This endpoint does not model elevation, traffic, or wind; it is a transparent arithmetic check, not a routing engine. Currency is whatever unit you use for fuel_price; the engine is unit-agnostic and does not convert dollars to euros. Missing required fields, non-finite values, and non-positive distance or economy all fail with invalid_input and are not charged after the engine rejects the request.

API usage, pricing, travel workflows, and practical limits

Call the free in-browser trip fuel cost estimator for vacation planning, classroom demos, and quick car comparisons without installing a spreadsheet. Send a JSON body with distance, fuel_economy, and fuel_price (or the documented aliases). Use the prepaid API when a travel portal, fleet dashboard, expense app, or booking tool needs a stable contract under KIT balance at $0.002 per successful item; validation failures never consume balance. Pair this endpoint with a fuel-price unit converter when the pump quote is per litre but your economy is in miles per gallon—convert the price first, then call here with matching units. For multi-leg itineraries, sum fuel_cost client-side or call once per leg so each segment stays auditable. Authors shipping SDKs can map fuel_needed and fuel_cost into tables that show volume and money side by side—the same shape drivers see on a simple road-trip budget sheet.