Commute Cost Worksheet: Know Your Real Driving Cost

Most of us could say what a tank of gas costs, but far fewer could say what it costs to drive to work and back for a month. This worksheet fixes that. Grab a pen or open a notes app and fill in the blanks below, one line at a time. By the end you will have your real cost per mile and your real cost per commute, which is the number you need before deciding whether sharing the ride makes sense.

Why a worksheet beats a guess

Guesses tend to stop at fuel. A worksheet forces you to include parking, tolls and the slow cost of wear, which are easy to forget because they arrive in separate bills. It also gives you a single number you can compare against anything else, whether that is a transit pass, a shared ride or your current routine.

You will need your last few fuel receipts or app records, your parking cost and a rough idea of your car's fuel economy. Round freely. An honest estimate that you finish beats a perfect one that you do not.

The fill-in-the-blanks worksheet

Work through the steps in order. The words in brackets tell you what to write on each line.

1. One-way commute miles. Check your trip distance in a maps app. Write it down: [____ miles].
2. Round-trip miles per day. Multiply line 1 by 2: [____ miles].
3. Commute days per month. Count the days you drive to the same place. Many people use 20 for a five-day week, but use your own number: [____ days].
4. Monthly commute miles. Multiply line 2 by line 3: [____ miles].
5. Miles per gallon. Use your car's real-world figure, which is often shown on the dashboard: [____ mpg].
6. Price per gallon. Use what you actually paid recently: [$____].
7. Fuel cost per mile. Divide line 6 by line 5: [$____ per mile].
8. Parking and tolls per day. Add daily parking and any tolls. If you pay monthly, divide by line 3: [$____].
9. Wear and tear per mile. Include tires, oil changes, brakes and repairs. Use your own records, or a modest allowance you are comfortable defending: [$____ per mile].
10. Total cost per mile (vehicle only). Add line 7 and line 9: [$____ per mile].
11. Cost per commute day. Multiply line 10 by line 2, then add line 8: [$____].
12. Cost per month. Multiply line 11 by line 3: [$____].

Line 10 is your real cost per mile for the commute, and line 11 is your real cost per commute day. Line 12 is the monthly bill you are paying to drive alone.

A quick example with made-up numbers

For example, suppose a commute is 12 miles each way, and the person drives 20 days a month. The car gets 30 miles per gallon, gas is $3.60 per gallon, and wear is allowed at $0.10 per mile. Parking is $5 per day.

• Round trip: 12 x 2 = 24 miles per day. Monthly miles: 24 x 20 = 480.
• Fuel per mile: $3.60 / 30 = $0.12.
• Total per mile: $0.12 + $0.10 = $0.22.
• Per commute day: 24 x $0.22 = $5.28, plus $5.00 parking = $10.28.
• Per month: $10.28 x 20 = $205.60.

These figures are invented to show the arithmetic, not typical costs. Your numbers will differ, and that is the point of filling in your own.

Compare your number to the IRS standard mileage rate

Once you have line 10, you can sanity check it against a public benchmark. The IRS publishes a standard mileage rate, a per-mile figure that it sets and updates over time. It is meant to approximate the cost of operating a vehicle, so it is a reasonable yardstick for your own number. We do not quote the figure here, because it changes. Look up the current rate on the IRS website.

If your own cost per mile is well below the published rate, check that you included every cost. If it is well above, look for the biggest line and see whether anything can be adjusted. This same rate is part of how ShareSpace Carpool caps ride prices; our post on IRS-compliant pricing explains the idea.

Whether and how the rate applies to your taxes is a tax question. Please ask a tax professional rather than relying on this worksheet.

What to do with your results

• Compare line 11 with a shared ride. As a rider, compare it with the total shown in the app before you confirm a booking. As a driver, compare it with the seat price you plan to set. Our savings framework shows how to do that comparison with two hypothetical cases.
• Find the largest line. If parking is the biggest piece, that is where a shared commute may help most.
• Redo it each season. Gas prices, parking rates and your car's age all change the answer.

Frequently asked questions

Should I include insurance and my car payment?

Those costs mostly exist whether or not you commute, so many people leave them out of a per-commute figure. If you want a fuller picture, you can add a share of them as extra lines. Your insurer can tell you how commuting affects your policy.

How do I estimate wear and tear?

Add up tires, oil changes, brakes and repairs from the last year and divide by the miles you drove. If you do not have records, pick a modest per-mile allowance and keep it the same when you compare options.

Is my result the amount a driver may charge riders?

No. On ShareSpace Carpool a driver's price per seat is capped to the shared cost of the trip, and the app shows the limit when you set the price. Your worksheet is a personal estimate of your own costs.

Put your number to work

Now that you know what your commute costs, see whether sharing it could lower the bill. Open ShareSpace Carpool to search for a ride or offer one, and compare the total you see in the app with line 11. If you are weighing options more broadly, read carpooling versus riding your own car.