Annual fuel cost calculator

How yearly fuel spending is computed from mileage, economy, and price

Yearly fuel spend is the volume of fuel a vehicle burns over a typical year multiplied by the price of one unit of that fuel. Volume is not a guess: it follows from annual mileage and fuel economy once you state how economy is written. Twelve thousand miles at twenty-eight miles per gallon needs about four hundred twenty-nine gallons; at three dollars and fifty cents per gallon the annual bill is one thousand five hundred dollars. Fifteen thousand kilometres at seven litres per one hundred kilometres needs one thousand fifty litres. When economy is distance per unit of fuel—miles per gallon or kilometres per litre—annual fuel volume equals annual_mileage divided by fuel_economy. When economy is consumption per distance—litres per one hundred kilometres or gallons per one hundred miles—annual fuel volume equals annual_mileage times fuel_economy divided by one hundred. Send required fields annual_mileage, fuel_economy, and fuel_price as JSON numbers or numeric strings. Optional economy_unit selects the identity: mpg (the default), km_per_l, l_per_100km, or gal_per_100mi. Optional tank_size, when positive, yields fillups_per_year so a household can see how often the tank is emptied. Aliases miles, km, annual_miles, annual_km, mileage, yearly_mileage, and distance map to annual_mileage; economy, mpg, km_per_l, efficiency, consumption, and fuel_efficiency map to fuel_economy; price, gas_price, price_per_unit, and fuel_unit_price map to fuel_price. Non-positive mileage or economy, a negative price, and an unknown economy_unit fail with invalid_input so a zero odometer or inverted sensor never produces a divide-by-zero or a nonsense credit. 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, choosing units, and using realistic inputs

Prefer a real-world average economy over an optimistic brochure figure when the year includes cold starts, hills, short urban hops, or highway speeds. On success the response echoes annual_mileage, fuel_economy, fuel_price, and economy_unit after stable rounding, plus annual_fuel_volume, annual_fuel_cost, monthly_fuel_cost, weekly_fuel_cost, daily_fuel_cost, cost_per_distance, a human-readable formula string, and method. Monthly is the yearly bill divided by twelve, weekly by fifty-two, and daily by three hundred sixty-five so a budget sheet can drop the same total into any calendar grain. cost_per_distance is the yearly bill divided by annual mileage—useful when you compare two cars at the same pump price, or when a reimbursement policy wants a fuel-only cents-per-mile check beside a statutory mileage rate. When tank_size is supplied, tank_size and fillups_per_year appear; those keys are omitted when you leave tank size out, so clients never see a null. Keep units coherent: miles with mpg or gal_per_100mi and a per-gallon price, or kilometres with km_per_l or l_per_100km and a per-litre price. This endpoint does not convert miles to kilometres or gallons to litres, and it does not look up live pump prices. Currency is whatever unit you use for fuel_price; the engine is unit-agnostic and never converts dollars to euros. Missing required fields, non-finite values, non-positive mileage or economy, a negative price, and an unknown economy_unit all fail with invalid_input and are not charged after the engine rejects the request.

API usage, pricing, vehicle-budget workflows, and practical limits

Call the free in-browser annual fuel cost calculator for household planning, car-shopping comparisons, and classroom demos without installing a spreadsheet. Send a JSON body with annual_mileage, fuel_economy, and fuel_price, plus optional economy_unit and tank_size (or the documented aliases). Use the prepaid API when a dealer desk, fleet dashboard, insurance quote, or personal-finance app needs a stable contract under KIT balance at $0.002 per successful item; validation failures never consume balance. Pair this endpoint with a fuel-economy converter when the window sticker is in litres per one hundred kilometres but your mileage log is in miles—convert first, then call here with matching units. For two vehicles, call twice at the same fuel_price and the same annual_mileage so the cost_per_distance fields are comparable. This calculator is a yearly running-cost slice, not a single-trip estimator: trip distance and one-journey cost belong on a different landing. Authors shipping SDKs can map annual_fuel_cost and monthly_fuel_cost into tables that sit next to insurance, parking, and service—the same shape drivers see on a simple total-cost-of-ownership sheet.