I read this question:

How to tell a colleague that I want to stop sharing the ride?

And I thought, maybe I don't pay my rideshare enough... Not the premise of that question, but it raised this question to me.

Taking into consideration:

• I would take public transport if not for being offered a lift which mean ridesharing saves me $a per day.




• Ridesharing gets me home around b minutes earlier.




• I jump out along the way which means there are c meters of extra distance due to me.




• The drive is long - d minutes, so that is certainly a factor.




• We have a similar level role - grunts. But that should probably be taken into account - perhaps e pay difference.

What is a good way to calculate the amount to offer a colleague who driveshares with me accounting for a, b c, d, e and the x factor which would probably be friendship?

In the US, there is a simple way to estimate the total cost without a lot of bookkeeping. The IRS has standard mileage rates for deducting business use of an automobile.

The 2018 business use rate, which includes cost of ownership, is 54.5 cents per mile. The moving rate, which only includes variable costs, is 18 cents per mile. I suggest picking one of those, or something in between, and paying half the IRS mileage rate.

Stop guessing, just ask

The only person who can really tell you how much it costs them, and how much they expect contributed - is the person you're ridesharing with.

Offering a specific amount risks either undervaluing them, or if the offer is higher than they'd expect - making them feel obligated to keep ridesharing with you.

Instead of trying to do any specific calculation, just mention that you are conscious there are a lot of hidden costs in running a car (including their time) and that you don't want them to feel like a bus service. Ask them to give you a number that they honestly feel covers the cost, and let them know that if circumstances ever change - they should just let you know.

Just expanding the point I made in comment as an answer. (Thank @Fattie for suggesting).

To me obvious thing is to share the fuel cost. (Calculating cost based on distance you are riding and the average fuel efficiency of that car's model and make). While calculating, always give benefit-of-doubt and rounding-off benefit to the car owner because there is some wear and tear on their car as well.

Having worked in different countries (but not ride-sharing), I know in general no one wants to make money from these arrangements. They just want to help out and feel good about making a difference on traffic and pollution situation. So I do no think you should compare it to taxi.

Also, no point in using hypothetical numbers as in how much money you would have spent if you would have taken public transport or how many minutes earlier or later you could have reached. You pay for how you are travelling now and not based how you could have travelled.

Also, another nice thing to do would be, once in a while may be buy them a lunch or invite them over for lunch (Depending on local culture at your location) to show your appreciation for the effort they are taking.

An easy answer is,

Use a taxi one day

and get that exact figure. ¹

The problem is you then have to calculate how much better it is to have your friend chauffeur you: it is much more convenient for you than a taxi.

So, multiply by say 1.5x or 2x.

One issue is I'm not sure whether you should use a "normal" taxi price or an "uber" price, which is usually less.

An issue with this...

This is sort of the "business" way to do it. But. It is very unrealistic.

• Say you are riding with friend every day


• Indeed it's likely that is the main use of the vehicle of friend


• Say you are paying via the formula mentioned above

Now, say that friend has a sudden repair - $900 for a new gearbox

• if you want to be "officious" about it, you would say "Oh, of course the amount I have been paying you every day includes such depreciation and a sinking cost factor. That guy on the internet said so. So, tough tittie for you! I'm not contributing a cent to the ghearbox! pick me up tomrorow ok!"

Of course, in reality you can't do that - in the example you have to give the guy half the cost of the new gearbox.

So the short answer is:

1. about what it would cost you to take a taxi




2. realistically as a polite person, you'll pay half of any "exceptional" costs that come up

¹ PagMax pointed out that of the taxi fare, a small amount is the taxi driver's earnings. (Maybe 20%.) Some people might feel that the share driver "shouldn't get" that.