Commute cost calculator

The engine is pure finite arithmetic with no network calls, no maps, and no date-dependent shortcuts, so the free browser tool and the API path always agree. Use it free on this page for a quick decision, or call the API at $0.002 per successful request when budgeting apps, relocation planners, or HR mobility tools need reproducible commute-cost comparisons.

What driving versus transit cost means in this calculator

Daily driving cost is the sum of fuel burned for the full workday distance and any parking you pay that day. Parking is added as a daily cash cost; if your garage is free, set parking to zero. One-way distance is multiplied by trips per day (two by default for a classic home-to-office-and-back pattern) to get daily_drive_distance. Fuel used that day is daily_drive_distance divided by fuel_efficiency, where efficiency is distance per unit of fuel such as miles per gallon or kilometres per litre—not litres per hundred kilometres. Fuel money is that volume times fuel_price in the same currency you use for parking and transit. Transit cost for the day is simply transit_fare: enter the total you actually pay for that commuting day, whether that is two one-way tickets, a day pass, or your fair share of a monthly pass divided by workdays. Monthly figures multiply each daily total by workdays_per_month (default twenty-two). The response also reports difference_daily and difference_monthly as driving minus transit, savings when the modes differ, and a cheaper label of driving, transit, or tie. There is no hidden toll model, insurance premium, vehicle depreciation, or carbon price: those matter in life but are outside this transparent fuel-plus-parking versus fare comparison. Negative distance or negative price fields fail with invalid_input rather than inventing a credit; non-positive fuel efficiency is rejected because division by zero or a negative mpg is not a meaningful vehicle economy.

Input contract, units, defaults, and error behaviour

Keep units consistent: if distance is in miles, use miles-per-gallon efficiency and price per gallon; if distance is in kilometres, use km per litre and price per litre. The calculator does not convert currencies or unit systems. Example: twelve miles one way, twenty-eight mpg, three point five currency units per gallon, fifteen parking, and six point five transit fare with defaults yields a clear pair of daily and monthly totals you can pin in tests. Failed validation is not billed. POST a JSON body with five required finite numbers: distance (one-way length in the same unit as efficiency), fuel_efficiency (positive distance per fuel unit), fuel_price (non-negative price per fuel unit), parking (non-negative daily parking), and transit_fare (non-negative full-day transit cost). Optional trips_per_day defaults to two; optional workdays_per_month defaults to twenty-two; both must be positive when provided. Numeric strings and plain JSON numbers are accepted; non-finite values, missing required fields, and empty strings fail with invalid_input naming the field. On success the body echoes the normalized inputs, daily_drive_distance, fuel_used_daily, drive_fuel_cost_daily, drive_cost_daily, transit_cost_daily, the monthly pair, difference and savings fields, cheaper, a formula string documenting the arithmetic, and precision used for rounding.

Where a commute cost compare API earns its keep

Keep distance and efficiency in matching units, document whether transit_fare is a day pass or two tickets, and you get reproducible comparisons for blogs, calculators, and edge workers without standing up mapping or payroll infrastructure of your own.