How this calculator works
The calculator doubles the one-way distance because a commute is normally travelled in both directions on every working day. Fuel use comes from the annual distance and fuel economy, and the fuel charge is that volume times the pump price. Parking and tolls are charged per commuting day, while wear and tear is charged per kilometre. The transit comparison assumes a monthly pass bought for all twelve months and one pass per person. It ignores the capital cost of the car, insurance and registration, because those are paid whether or not you drive to work.
Formula
Annual distance = one-way distance x 2 x commuting days. Fuel = annual distance / fuel economy (km/L). Annual driving cost = fuel x price + parking per day x days + wear per km x annual distance. Cost per person divides by the number of riders. Transit saving = driving cost per person - 12 x monthly pass.
Worked example
A 15 km one-way commute on 235 days covers 7,050 km. At 8 L/100 km the car uses 564 L, costing $930.60 at $1.65 a litre. Parking at $8 a day adds $1,880 and wear at $0.12 a kilometre adds $846, for $3,656.60 a year. A $156 monthly pass costs $1,872, so transit saves $1,784.60 per person.
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Frequently asked questions
Should I include car insurance and depreciation?
The page includes wear and tear, which is a running-cost allowance. Insurance and registration are usually fixed whether you drive or not, so they are left out of the driving-versus-transit comparison. Add them through the wear rate if you want a full ownership cost.
Why is the transit comparison negative sometimes?
A negative saving means the yearly transit pass costs more than driving at the entered prices. Try the actual pass price, include parking and tolls, and use a realistic wear rate before deciding.
What wear rate should I use?
A simple allowance is a few cents per kilometre for tires, brakes, fluids and depreciation. Use your own maintenance records divided by the kilometres driven for a figure that matches your vehicle.
Does carpooling change the transit comparison?
The driving cost per person falls as more riders share, so the saving with transit shrinks. Enter the number of people who would actually split the driving cost, not the total number of passengers.