Math behind it all
We researched the web and we found the average amount of Carbon Dioxide (CO2) generated by varied modes of travel. We computed the amount of CO2 that your travel generated:
Entire Amount of CO2 = 1.621 * miles by plane + 0.632 * miles by car + 0.04267 * miles by train + 1.869 * miles by boat
Then we applied the price you chose for 1000 lb of CO2 for the entire trip:
Your Carbon Offset = (your price for 1000 lb of CO2) * (1.621 * plane + 0.632 * car + 0.04267 * train + 1.869 * boat)/1000