In addition, most calculators seem to think that riding a bike has zero cost. But, if you ride like I do, meaning you actually put tubes and tires on your rims, you do in fact consume something that costs money to replace. In addition, many peoples' bike commute utilizes a "bus boost" in one or both directions, which also usually costs money.
This calculator attempts to estimate a more realistic comparison, and is likely to be disappointing to bicycle advocates. However, using the typical comparison is highly misleading and not particularly useful in policy discussions. For instance, it becomes pretty clear that the variable cost of driving is not very expensive compared to the alternatives, which points to a major problem in current transportation economics.
For my calculation (when I take the express bus in the morning), click here. And if you can make a strong argument that my default costs are wrong, please email me.