How do I calculate how much to charge for car pooling? I own my car and get 32 mpg city and 37 Hwy. I currently may have just one additional rider.

The IRS has a standard calculation of what can be deducted for business mileage. Many buisinesses use that as their standard for reimbursements. So I think you can use it as your cost to determine car polling shares. I believe they just raised it to 58.5 cents per mile, but you can check at Internal Revenue Service for the exact amount.